On 27 Oct 1889 [his father] Constantine I King Greece (age 21) and [his mother] Sophia Hohenzollern Queen Consort Greece (age 19) were married. She the daughter of Frederick III King Prussia and Victoria Empress Germany Queen Consort Prussia (age 48). He the son of George I King Greece 1845-1913 (age 43) and Olga Constantinovna Holstein Gottorp Romanov Queen Consort Greece (age 38). They were half second cousin once removed. He a great x 4 grandson of King George II of Great Britain and Ireland. She a granddaughter of Queen Victoria of the United Kingdom. 
On 14 Dec 1901 Paul I King Greece was born to Constantine I King Greece (age 33) and Sophia Hohenzollern Queen Consort Greece (age 31). He a great grandson of Queen Victoria of the United Kingdom.
On 18 Mar 1913 [his grandfather] George I King Greece 1845-1913 (age 67) died. His son [his father] Constantine I King Greece (age 44) succeeded I King Greece. [his mother] Sophia Hohenzollern Queen Consort Greece (age 42) by marriage Queen Consort Greece.
On 25 Oct 1920 [his brother] Alexander I King Greece 1893-1920 (age 27) died. His brother Paul I King Greece (age 18) succeeded I King Greece.
On 11 Jan 1923 [his father] Constantine I King Greece (age 54) died.
On 13 Jan 1932 [his mother] Sophia Hohenzollern Queen Consort Greece (age 61) died.
In 1938 Paul I King Greece (age 36) and Frederica Hanover Queen Consort Greece (age 20) were married. She by marriage Queen Consort Greece. She the daughter of Ernest Augustus Hanover Duke Brunswick 1887-1953 (age 50) and Viktoria Luise Hohenzollern Duchess Brunswick (age 45). He the son of Constantine I King Greece and Sophia Hohenzollern Queen Consort Greece. They were second cousins. He a great grandson of Queen Victoria of the United Kingdom. She a great x 2 granddaughter of Queen Victoria of the United Kingdom.
In 1938 [his daughter] Sophia Glücksburg Queen Consort Spain was born to Paul I King Greece (age 36) and [his wife] Frederica Hanover Queen Consort Greece (age 20). She a great x 2 granddaughter of Queen Victoria of the United Kingdom. Coefficient of inbreeding 5.26%.
On 02 Jun 1940 [his son] Constantine II King Hellenes 1940- was born to Paul I King Greece (age 38) and [his wife] Frederica Hanover Queen Consort Greece (age 23). He a great x 2 grandson of Queen Victoria of the United Kingdom. Coefficient of inbreeding 5.26%.
In 1942 [his daughter] Irene Glücksburg was born to Paul I King Greece (age 40) and [his wife] Frederica Hanover Queen Consort Greece (age 24). She a great x 2 granddaughter of Queen Victoria of the United Kingdom. Coefficient of inbreeding 5.26%.
In 1946 [his brother-in-law] George William Hanover (age 30) and Sophie Glücksburg (age 31) were married. He the son of Ernest Augustus Hanover Duke Brunswick 1887-1953 (age 58) and Viktoria Luise Hohenzollern Duchess Brunswick (age 53). They were second cousins. He a great x 2 grandson of Queen Victoria of the United Kingdom. She a great x 2 granddaughter of Queen Victoria of the United Kingdom.
In 1951 [his brother-in-law] Ernest Augustus Hanover (age 36) and Ortrud Schleswig Holstein Sonderburg Glücksburg were married. He the son of Ernest Augustus Hanover Duke Brunswick 1887-1953 (age 63) and Viktoria Luise Hohenzollern Duchess Brunswick (age 58). He a great x 2 grandson of Queen Victoria of the United Kingdom.
In 1960 [his brother-in-law] Welf Henry Hanover (age 36) and Alexandra Unknown were married. He the son of Ernest Augustus Hanover Duke Brunswick 1887-1953 and Viktoria Luise Hohenzollern Duchess Brunswick (age 67). He a great x 2 grandson of Queen Victoria of the United Kingdom.
In 1962 [his son-in-law] Juan Carlos I King Spain 1938- (age 23) and [his daughter] Sophia Glücksburg Queen Consort Spain (age 24) were married. She by marriage Queen Consort Spain. She the daughter of Paul I King Greece 1901-1964 (age 60) and Frederica Hanover Queen Consort Greece (age 44). They were third cousins. He a great x 2 grandson of Queen Victoria of the United Kingdom. She a great x 2 granddaughter of Queen Victoria of the United Kingdom. 
In 1963 [his brother-in-law] Christian Oscar Hanover (age 43) and Mireille Dutry were married. He the son of Ernest Augustus Hanover Duke Brunswick 1887-1953 and Viktoria Luise Hohenzollern Duchess Brunswick (age 70). He a great x 2 grandson of Queen Victoria of the United Kingdom.
On 06 Mar 1964 Paul I King Greece (age 62) died.
On 06 Feb 1981 [his former wife] Frederica Hanover Queen Consort Greece (age 63) died.
Paternal Family Tree: Oldenburg
Maternal Family Tree: Marie Elisabeth of Saxony Duchess Holstein Gottorp 1610-1684
Kings Wessex: Great x 25 Grand Son of King Edmund "Ironside" I of England
Kings Gwynedd: Great x 23 Grand Son of Owain "Great" King Gwynedd 1100-1170
Kings Seisyllwg: Great x 29 Grand Son of Hywel "Dda aka Good" King Seisyllwg King Deheubarth
Kings Powys: Great x 24 Grand Son of Maredudd ap Bleddyn King Powys 1047-1132
Kings England: Great Grand Son of Queen Victoria of the United Kingdom
Kings Scotland: Great x 19 Grand Son of Robert "The Bruce" I King Scotland
Kings Franks: Great x 21 Grand Son of Louis VII King Franks
Kings France: Great x 16 Grand Son of Charles "Beloved Mad" VI King France
Great x 4 Grandfather: Karl Anton Oldenburg I Duke Schleswig-Holstein-Sonderburg-Beck -1759 16 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 3 Grandfather: Friedrich Karl Ludwig Oldenburg I Duke Schleswig-Holstein-Sonderburg-Beck 1757-1816 17 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandmother: Frederica Charlotte Dohna Schlodien Duchess Schleswig-Holstein-Sonderburg-Beck
Great x 2 Grandfather: Friedrich Wilhelm Glücksburg Duke Schleswig Holstein Sonderburg Glücksburg 1785-1831 18 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 3 Grandmother: Friederike Schlieben Duchess Schleswig-Holstein-Sonderburg-Beck
Great x 1 Grandfather: King Christian IX of Denmark 1818-1906 2 x Great Grand Son of King George II of Great Britain and Ireland
Great x 4 Grandfather: Frederick Hesse-Kassel 14 x Great Grand Son of King Henry III of England
Great x 3 Grandfather: Charles Hesse-Kassel Grand Son of King George II of Great Britain and Ireland
Great x 4 Grandmother: Mary Hanover Daughter of King George II of Great Britain and Ireland
Great x 2 Grandmother: Louise Caroline Hesse-Kassel Duchess Schleswig Holstein Sonderburg Glücksburg Great Grand Daughter of King George II of Great Britain and Ireland
Great x 4 Grandfather: Frederick V King Denmark and Norway 1723-1766 15 x Great Grand Son of King Henry III of England
Great x 3 Grandmother: Louise Oldenburg Grand Daughter of King George II of Great Britain and Ireland
Great x 4 Grandmother: Louise Hanover Queen Consort Denmark and Norway Daughter of King George II of Great Britain and Ireland
GrandFather: George I King Greece 1845-1913 3 x Great Grand Son of King George II of Great Britain and Ireland
Great x 4 Grandfather: Frederick Hesse-Kassel 14 x Great Grand Son of King Henry III of England
Great x 3 Grandfather: Frederick Hesse-Kassel Grand Son of King George II of Great Britain and Ireland
Great x 4 Grandmother: Mary Hanover Daughter of King George II of Great Britain and Ireland
Great x 2 Grandfather: William Hesse-Kassel Great Grand Son of King George II of Great Britain and Ireland
Great x 1 Grandmother: Queen Louise Hesse-Kassel of Denmark 2 x Great Grand Daughter of King George II of Great Britain and Ireland
Great x 4 Grandfather: Frederick V King Denmark and Norway 1723-1766 15 x Great Grand Son of King Henry III of England
Great x 3 Grandfather: Prince Frederick Oldenburg 16 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandmother: Juliana Maria Welf Queen Consort Denmark and Norway 15 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 2 Grandmother: Princess Charlotte of Denmark 17 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 4 Grandfather: Duke Louis of Mecklenburg-Schwerin 15 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 3 Grandmother: Duchess Sophia Frederica of Mecklenburg-Schwerin 16 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 4 Grandmother: Charlotte Sophie Saxe Coburg Saalfeld 16 x Great Grand Daughter of King Henry "Curtmantle" II of England
Father: Constantine I King Greece 4 x Great Grand Son of King George II of Great Britain and Ireland
Great x 4 Grandfather: Peter III of Russia 17 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 3 Grandfather: Paul Emperor of Russia 18 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 2 Grandfather: Tsar Nicholas I of Russia 3 x Great Grand Son of King George I of Great Britain and Ireland
Great x 4 Grandfather: Frederick Eugene Württemberg Duke Württemberg
Great x 3 Grandmother: Empress Sophie Dorothea of Russia 2 x Great Grand Daughter of King George I of Great Britain and Ireland
Great x 4 Grandmother: Friederike Sophie Dorothea Hohenzollern Great Grand Daughter of King George I of Great Britain and Ireland
Great x 1 Grandfather: Konstantin Nikolayevich Holstein Gottorp Romanov 4 x Great Grand Son of King George I of Great Britain and Ireland
Great x 4 Grandfather: Frederick William II King Prussia 1744-1797 Great Grand Son of King George I of Great Britain and Ireland
Great x 3 Grandfather: Frederick William II King Prussia 1770-1840 2 x Great Grand Son of King George I of Great Britain and Ireland
Great x 4 Grandmother: Queen Frederica Louisa of Prussia 17 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 2 Grandmother: Charlotte Hohenzollern 3 x Great Grand Daughter of King George I of Great Britain and Ireland
GrandMother: Olga Constantinovna Holstein Gottorp Romanov Queen Consort Greece 5 x Great Grand Daughter of King George I of Great Britain and Ireland
Paul I King Greece 1901-1964 Great Grand Son of Queen Victoria of the United Kingdom
Great x 4 Grandfather: Augustus William Hohenzollern Grand Son of King George I of Great Britain and Ireland
Great x 3 Grandfather: Frederick William II King Prussia 1744-1797 Great Grand Son of King George I of Great Britain and Ireland
Great x 2 Grandfather: Frederick William II King Prussia 1770-1840 2 x Great Grand Son of King George I of Great Britain and Ireland
Great x 4 Grandfather: Landgrave Louis IX of Hesse-Darmstadt 16 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 3 Grandmother: Queen Frederica Louisa of Prussia 17 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 4 Grandmother: Countess Palatine Caroline of Zweibrücken
Great x 1 Grandfather: William I King Prussia 1797-1888 3 x Great Grand Son of King George I of Great Britain and Ireland
GrandFather: Frederick III King Prussia 4 x Great Grand Son of King George I of Great Britain and Ireland
Mother: Sophia Hohenzollern Queen Consort Greece Grand Daughter of Queen Victoria of the United Kingdom
Great x 4 Grandfather: Ernest Frederick Saxe Coburg Saalfeld Duke Saxe Coburg Saalfeld 1724-1800 16 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 3 Grandfather: Francis Saxe Coburg Gotha I Duke Saxe Coburg Gotha 1750-1806 16 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandmother: Sophia Antonia Brunswick-Wolfenbüttel Duchess Saxe Coburg Saalfeld 15 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 2 Grandfather: Ernest Saxe Coburg Gotha I Duke Saxe Coburg Gotha 17 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandfather: Heinrich XXIV Count Reuss of Ebersdorf
Great x 3 Grandmother: Augusta Reuss Duchess Saxe Coburg Gotha 17 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 4 Grandmother: Karoline Ernestine of Erbach Schonberg 16 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 1 Grandfather: Prince Albert Saxe Coburg Gotha 18 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandfather: Duke Ernest of Saxe Coburg Altenburg 1745-1804 17 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 3 Grandfather: Duke Augustus of Saxe Coburg Altenburg 1772-1822 18 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandmother: Charlotte Saxe Meiningen Duchess Saxe Gotha Altenburg
Great x 2 Grandmother: Duchess Louise Dorothea of Saxe Coburg Altenburg 18 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 4 Grandfather: Grand Duke Frederick Francis I of Mecklenburg-Schwerin 16 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 3 Grandmother: Louise Charlotte Mecklenburg-Schwerin 17 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 4 Grandmother: Princess Louise of Saxe-Gotha-Altenburg 17 x Great Grand Daughter of King Henry "Curtmantle" II of England
GrandMother: Victoria Empress Germany Queen Consort Prussia Daughter of Queen Victoria of the United Kingdom
Great x 4 Grandfather: Frederick Louis Hanover Prince of Wales Son of King George II of Great Britain and Ireland
Great x 3 Grandfather: King George III of Great Britain and Ireland Grand Son of King George II of Great Britain and Ireland
Great x 4 Grandmother: Augusta Saxe Coburg Altenburg 16 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 2 Grandfather: Edward Augustus Hanover 1st Duke Kent and Strathearn Son of King George III of Great Britain and Ireland
Great x 4 Grandfather: Charles Louis Frederick Duke of Mecklenburg 14 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 3 Grandmother: Charlotte Mecklenburg Strelitz Queen Consort England 15 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 1 Grandmother: Queen Victoria of the United Kingdom Grand Daughter of King George III of Great Britain and Ireland
Great x 4 Grandfather: Ernest Frederick Saxe Coburg Saalfeld Duke Saxe Coburg Saalfeld 1724-1800 16 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 3 Grandfather: Francis Saxe Coburg Gotha I Duke Saxe Coburg Gotha 1750-1806 16 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandmother: Sophia Antonia Brunswick-Wolfenbüttel Duchess Saxe Coburg Saalfeld 15 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 2 Grandmother: Marie Luise Victoria Saxe Coburg Gotha Duchess Kent and Strathearn 17 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 4 Grandfather: Heinrich XXIV Count Reuss of Ebersdorf
Great x 3 Grandmother: Augusta Reuss Duchess Saxe Coburg Gotha 17 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 4 Grandmother: Karoline Ernestine of Erbach Schonberg 16 x Great Grand Daughter of King Henry "Curtmantle" II of England