On 11 Sep 1856 [his father] Frederick Christian Oldenburg II Duke Schleswig Holstein Sonderburg Augustenburg 1829-1880 (age 27) and [his mother] Adelheid Hohenlohe Langenburg Duchess Schleswig Holstein Sonderburg Augustenburg were married. She by marriage Duchess Schleswig Holstein Sonderburg Augustenburg. He the son of Christian August Oldenburg II Duke Schleswig Holstein Sonderburg Augustenburg 1798-1869 (age 58) and Louise Sophie Danneskiold Samsøe Duchess Schleswig Holstein Sonderburg Augustenburg. He a great x 3 grandson of King George II of Great Britain and Ireland. 
On 11 Aug 1863 Ernst Gunther Oldenburg Duke Schleswig Holstein Sonderburg Augustenburg was born to Frederick Christian Oldenburg II Duke Schleswig Holstein Sonderburg Augustenburg 1829-1880 (age 34) and Adelheid Hohenlohe Langenburg Duchess Schleswig Holstein Sonderburg Augustenburg.
On 11 Mar 1869 [his grandfather] Christian August Oldenburg II Duke Schleswig Holstein Sonderburg Augustenburg 1798-1869 (age 70) died. His son [his father] Frederick Christian Oldenburg II Duke Schleswig Holstein Sonderburg Augustenburg 1829-1880 (age 39) succeeded II Duke Schleswig Holstein Sonderburg Augustenburg.
On 14 Jan 1880 [his father] Frederick Christian Oldenburg II Duke Schleswig Holstein Sonderburg Augustenburg 1829-1880 (age 50) died. His son Ernst Gunther Oldenburg Duke Schleswig Holstein Sonderburg Augustenburg (age 16) succeeded Gunther Duke Schleswig Holstein Sonderburg Augustenburg.
On 02 Aug 1898 Ernst Gunther Oldenburg Duke Schleswig Holstein Sonderburg Augustenburg (age 34) and Dorothea Maria Saxe Coburg Gotha Duchess Schleswig Holstein Sonderburg Augustenburg (age 17) were married. She by marriage Duchess Schleswig Holstein Sonderburg Augustenburg. He the son of Frederick Christian Oldenburg II Duke Schleswig Holstein Sonderburg Augustenburg 1829-1880 and Adelheid Hohenlohe Langenburg Duchess Schleswig Holstein Sonderburg Augustenburg. He a great x 4 grandson of King George II of Great Britain and Ireland.
On 27 Apr 1916 [his brother-in-law] Leopold Clement Saxe Coburg Gotha (age 37) died after six months of suffering following his attack by Camilla Rybicka.
On 21 Feb 1921 Ernst Gunther Oldenburg Duke Schleswig Holstein Sonderburg Augustenburg (age 57) died.
On 21 Jan 1967 [his former wife] Dorothea Maria Saxe Coburg Gotha Duchess Schleswig Holstein Sonderburg Augustenburg (age 85) died.
Paternal Family Tree: Oldenburg
Maternal Family Tree: Adelheid Hohenlohe Langenburg Duchess Schleswig Holstein Sonderburg Augustenburg
Kings Wessex: Great x 25 Grand Son of King Edmund "Ironside" I of England
Kings Gwynedd: Great x 22 Grand Son of Owain "Great" King Gwynedd 1100-1170
Kings Seisyllwg: Great x 28 Grand Son of Hywel "Dda aka Good" King Seisyllwg King Deheubarth
Kings Powys: Great x 23 Grand Son of Maredudd ap Bleddyn King Powys 1047-1132
Kings England: Great x 4 Grand Son of King George II of Great Britain and Ireland
Kings Scotland: Great x 18 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 15 Grand Son of Charles "Beloved Mad" VI King France
Great x 4 Grandfather: Frederick William Oldenburg I Duke Schleswig Holstein Sonderburg Augustenburg 1668-1714 14 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 3 Grandfather: Christian August Oldenburg I Duke Schleswig Holstein Sonderburg Augustenburg 1696-1754 15 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 2 Grandfather: Frederick Christian Oldenburg I Duke Schleswig Holstein Sonderburg Augustenburg 1721-1794 16 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 1 Grandfather: Frederick Christian Oldenburg II Duke Schleswig Holstein Sonderburg Augustenburg 1765-1814 17 x Great Grand Son of King Henry "Curtmantle" II of England
GrandFather: Christian August Oldenburg II Duke Schleswig Holstein Sonderburg Augustenburg 1798-1869 2 x Great Grand Son of King George II of Great Britain and Ireland
Great x 4 Grandfather: Christian VI King Denmark and Norway 1699-1746 14 x Great Grand Son of King Henry III of England
Great x 3 Grandfather: Frederick V King Denmark and Norway 1723-1766 15 x Great Grand Son of King Henry III of England
Great x 2 Grandfather: Christian VII King Denmark and Norway 1749-1808 Grand Son of King George II of Great Britain and Ireland
Great x 4 Grandfather: King George II of Great Britain and Ireland Son of King George I of Great Britain and Ireland
Great x 3 Grandmother: Louise Hanover Queen Consort Denmark and Norway Daughter of King George II of Great Britain and Ireland
Great x 4 Grandmother: Caroline Hohenzollern Queen Consort England 15 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 1 Grandmother: Louise Auguste possible father Johann Friedrich Struensee Oldenburg Duchess Schleswig Holstein Sonderburg Augustenburg Great Grand Daughter of King George II of Great Britain and Ireland
Great x 4 Grandfather: King George II of Great Britain and Ireland Son of King George I of Great Britain and Ireland
Great x 3 Grandfather: Frederick Louis Hanover Prince of Wales Son of King George II of Great Britain and Ireland
Great x 4 Grandmother: Caroline Hohenzollern Queen Consort England 15 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 2 Grandmother: Caroline Matilda Hanover Queen Consort Denmark and Norway Grand Daughter of King George II of Great Britain and Ireland
Great x 4 Grandfather: Frederick Saxe Coburg Altenburg II Duke Saxe Gotha Altenburg 1676-1732 15 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 3 Grandmother: Augusta Saxe Coburg Altenburg 16 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 4 Grandmother: Magdalena Augusta Anhalt Zerbst Anhaltzerbst Duchess Saxe Gotha Altenburg
Father: Frederick Christian Oldenburg II Duke Schleswig Holstein Sonderburg Augustenburg 1829-1880 3 x Great Grand Son of King George II of Great Britain and Ireland
GrandMother: Louise Sophie Danneskiold Samsøe Duchess Schleswig Holstein Sonderburg Augustenburg
Ernst Gunther Oldenburg Duke Schleswig Holstein Sonderburg Augustenburg 1863-1921 4 x Great Grand Son of King George II of Great Britain and Ireland
Mother: Adelheid Hohenlohe Langenburg Duchess Schleswig Holstein Sonderburg Augustenburg