Isabella Stewart Countess Douglas was born to King Robert II of Scotland and .
In 1336 [her father] King Robert II of Scotland (age 19) and [her mother] were married. She by marriage Queen Consort Scotland. She had been his mistress for a number of years. He a great x 3 grandson of King John "Lackland" of England.
Around 1356 [her father] King Robert II of Scotland (age 39) and were married. She by marriage Queen Consort Scotland. She the daughter of and . He a great x 3 grandson of King John "Lackland" of England. 
On 22 Feb 1371 King David II of Scotland (age 46) died without issue at Edinburgh Castle [Map]. He was buried at Holyrood Abbey. His nephew [her father] King Robert II of Scotland (age 54) succeeded II King Scotland. He, David, was the last of the male line of the House of Bruce. Robert (age 54), the first of the House of Stewart, being the son of his sister [her grandmother] Marjory Bruce who had married [her grandfather] Walter Stewart 6th High Steward.
On 19 Apr 1390 [her father] King Robert II of Scotland (age 74) died at Dundonald Castle, Dundonald. He was buried at Scone Abbey [Map]. His son [her brother] King Robert III of Scotland 1337-1406 (age 53) succeeded III King Scotland. (age 40) by marriage Queen Consort Scotland. His son [her half-brother] David Stewart 3rd Earl Strathearn 1st Earl Caithness succeeded 3rd Earl Strathearn.
In 1410 Isabella Stewart Countess Douglas died.
David Edmonstone and Isabella Stewart Countess Douglas were married. She the daughter of King Robert II of Scotland and . She a great x 4 granddaughter of King John "Lackland" of England.
James Douglas 2nd Earl Douglas and Isabella Stewart Countess Douglas were married. She by marriage Countess Douglas. She the daughter of King Robert II of Scotland and . He the son of William Douglas 1st Earl Douglas and . They were half third cousin once removed. She a great x 4 granddaughter of King John "Lackland" of England. 
Paternal Family Tree: Stewart
Descendants Family Trees:
Kings Wessex: Great x 9 Grand Daughter of King Edmund "Ironside" I of England
Kings Gwynedd: Great x 5 Grand Daughter of Owain "Great" King Gwynedd 1100-1170
Kings Seisyllwg: Great x 11 Grand Daughter of Hywel "Dda aka Good" King Seisyllwg King Deheubarth
Kings Powys: Great x 6 Grand Daughter of Maredudd ap Bleddyn King Powys 1047-1132
Kings England: Great x 4 Grand Daughter of King John "Lackland" of England
Kings Scotland: Great Grand Daughter of Robert "The Bruce" I King Scotland
Kings Franks: Great x 16 Grand Daughter of Louis "Pious" King Aquitaine I King Franks
Kings France: Great x 9 Grand Daughter of Robert "Pious" II King France
Great x 4 Grandfather: Alan Fitzwalter 2nd High Steward
Great x 3 Grandfather: Walter Stewart 3rd High Steward
Great x 2 Grandfather: Alexander Stewart 4th High Steward
Great x 3 Grandmother: Bethóc Angus
Great x 4 Grandmother: Marjorie Dunkeld Countess Angus
Great x 1 Grandfather: James Stewart 5th High Steward
GrandFather: Walter Stewart 6th High Steward
Father: King Robert II of Scotland 3 x Great Grand Son of King John "Lackland" of England
Great x 4 Grandfather: Robert Bruce 4th Lord Annandale
Great x 3 Grandfather: Robert Bruce 5th Lord Annandale 4 x Great Grand Son of King Henry I "Beauclerc" England
Great x 4 Grandmother: Isabel "the Scot" Dunkeld Lady Annandale 3 x Great Grand Daughter of King Henry I "Beauclerc" England
Great x 2 Grandfather: Robert Bruce Earl Carrick 1243-1304 4 x Great Grand Son of King Henry I "Beauclerc" England
Great x 4 Grandfather: Gilbert Clare 5th Earl Gloucester 4th Earl Hertford
2 x Great Grand Son of King Henry I "Beauclerc" England
Great x 3 Grandmother: Isabel Clare Lady Annandale 3 x Great Grand Daughter of King Henry I "Beauclerc" England
Great x 4 Grandmother: Isabel Marshal Countess Cornwall, Gloucester and Hertford 1200-1240
Great x 1 Grandfather: Robert "The Bruce" I King Scotland 5 x Great Grand Son of King Henry I "Beauclerc" England
Great x 4 Grandfather: Walter Stewart 3rd High Steward
Great x 3 Grandmother: Margaret Stewart Countess Carrick
Great x 4 Grandmother: Bethóc Angus
GrandMother: Marjory Bruce 2 x Great Grand Daughter of King John "Lackland" of England
Great x 1 Grandmother: Isabella Mar Great Grand Daughter of King John "Lackland" of England
Great x 4 Grandfather: Iorwerth "Drwyndwn aka Flat Nosed" Aberffraw
Great x 3 Grandfather: Llewellyn "The Great" Aberffraw
Great x 4 Grandmother: Marared ferch Madog Mathrafal
Great x 2 Grandmother: Elen ferch Llewellyn Aberffraw Countess Huntingdon and Mar Grand Daughter of King John "Lackland" of England
Great x 4 Grandfather: King John "Lackland" of England
Son of King Henry "Curtmantle" II of England
Great x 3 Grandmother: Joan Plantagenet Daughter of King John "Lackland" of England
Great x 4 Grandmother: Adela Plantagenet
Isabella Stewart Countess Douglas -1410 4 x Great Grand Daughter of King John "Lackland" of England