Biography of Walter Stewart 1st Earl Atholl 3rd Earl Caithness 1360-1437
Paternal Family Tree: Stewart
Maternal Family Tree: Margaret Graham Countess Ross
In 1336 [his father] King Robert II of Scotland (age 19) and Elizabeth Mure Queen Consort Scotland 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 [his father] King Robert II of Scotland (age 39) and [his mother] Euphemia Ross Queen Consort Scotland were married. She by marriage Queen Consort Scotland. She the daughter of Hugh 4th Earl Ross and Margaret Graham Countess Ross. He a great x 3 grandson of King John "Lackland" of England. 
Around 1360 Walter Stewart 1st Earl Atholl 3rd Earl Caithness was born to King Robert II of Scotland (age 43) and Euphemia Ross Queen Consort Scotland.
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 [his 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 [his grandmother] Marjory Bruce who had married [his grandfather] Walter Stewart 6th High Steward.
In 1390 Eupheme Stewart 2nd Countess of Strathearn and Caithness resigned the title 2nd Countess Caithness to her uncle Walter Stewart 1st Earl Atholl 3rd Earl Caithness (age 30) who became 3rd Earl Caithness.
On 19 Apr 1390 [his father] King Robert II of Scotland (age 74) died at Dundonald Castle, Dundonald. He was buried at Scone Abbey [Map]. His son [his half-brother] King Robert III of Scotland (age 53) succeeded III King Scotland. Anabella Drummond Queen Consort Scotland (age 40) by marriage Queen Consort Scotland. His son [his brother] David Stewart 3rd Earl Strathearn 1st Earl Caithness succeeded 3rd Earl Strathearn.
In 1404 Walter Stewart 1st Earl Atholl 3rd Earl Caithness (age 44) was created 1st Earl Atholl.
On 18 May 1425 Murdoch Stewart 2nd Duke Albany (age 63), his two sons Walter Stewart (age 25) and Alexander Stewart, and Duncan Lennox 8th Earl Lennox (age 80) were tried at Stirling Castle [Map] in the presence of King James I of Scotland (age 30).
The jury which condemned them was composed of 21 knights and peers, including Albany's (age 63) half-uncle Walter Stewart 1st Earl Atholl 3rd Earl Caithness (age 65), first cousin Alexander Stewart 1st Earl Mar (age 50), first cousins once-removed Archibald Douglas 2nd Duke Touraine (age 35), and Alexander, Earl of Ross and Lord of the Isles.
In 1428 Walter Stewart 1st Earl Atholl 3rd Earl Caithness (age 68) resigned the Earldom of Caithness to his son [his son] Allan Stewart 4th Earl Caithness.
In 1431 [his son] Allan Stewart 4th Earl Caithness died. Earl Caithness returned to Walter Stewart 1st Earl Atholl 3rd Earl Caithness (age 71).
On 26 Mar 1437 Walter Stewart 1st Earl Atholl 3rd Earl Caithness (age 77) was hanged, drawn and quartered at Edinburgh Castle [Map] for having conspired to assassinate King James I of Scotland (deceased). He had unbarred the doors to the royal apartments, permitting assassins to enter the King's lodging. Earl Atholl and Earl Caithness forfeit by attainder.
John Randolph 3rd Earl Moray and [his mother] Euphemia Ross Queen Consort Scotland were married. She by marriage Countess Moray. She the daughter of Hugh 4th Earl Ross and Margaret Graham Countess Ross. He the son of Thomas Randolph 1st Earl Moray and Isabella Stewart Countess Moray.
[his son] Allan Stewart 4th Earl Caithness was born to Walter Stewart 1st Earl Atholl 3rd Earl Caithness.
Kings Wessex: Great x 9 Grand Son of King Edmund "Ironside" I of England
Kings Gwynedd: Great x 5 Grand Son of Owain "Great" King Gwynedd
Kings Seisyllwg: Great x 11 Grand Son of Hywel "Dda aka Good" King Seisyllwg King Deheubarth
Kings Powys: Great x 6 Grand Son of Maredudd ap Bleddyn King Powys
Kings England: Great x 4 Grand Son of King John "Lackland" of England
Kings Scotland: Great Grand Son of Robert "The Bruce" I King Scotland
Kings Franks: Great x 16 Grand Son of Louis "Pious" King Aquitaine I King Franks
Kings France: Great x 9 Grand Son 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 4 Grandfather: Gille Críst Angus 4th Earl Angus
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 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
Great x 1 Grandfather: Robert "The Bruce" I King Scotland 5 x Great Grand Son of King Henry I "Beauclerc" England
Great x 3 Grandfather: Niall Carrick 2nd Earl Carrick
Great x 2 Grandmother: Marjorie Carrick 3rd Countess Carrick
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 3 Grandfather: Donald Mar 6th Earl Mar
Great x 2 Grandfather: Donald Mar 7th Earl Mar
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
Walter Stewart 1st Earl Atholl 3rd Earl Caithness 4 x Great Grand Son of King John "Lackland" of England
GrandFather: Hugh 4th Earl Ross
Mother: Euphemia Ross Queen Consort Scotland
Great x 1 Grandfather: John Graham of Abercorn
GrandMother: Margaret Graham Countess Ross