He had a relationship with Elen (Helen) ferch Llywelyn.
Child(ren):
From https://www.geni.com/people/Donald-de-Mar-6th-Earl-of-Mar Donald (Sir),6th Earl of Mar; knighted 1270; one of the leading Scottish nobles who recognised Alexander III's daughter Margaret as heir to the throne after her father's death Feb 1283/4; following Margaret's death 1290 supported Robert the Bruce but was one of the seven Earls of Scotland who referred a decision in the matter to Edward I of England, to whom he swore fealty as overlord 13 June 1291; nevertheless was a leading participant in the Scottish Uprising against the English shortly afterwards, being captured by them following the Battle of Dunbar 27 April 1296 and renewing his allegiance to Edward I thereafter. [Burke's Peerage]Domhnall I Earl of Mar - Domhnall mac Uilleim (Donald, William's son) - was the seventh known Mormaer of Mar, ruling from 1276 until his death somewhere between 1297 and 1302.
Domhnall was a strong supporter of the Bruce cause during the crisis of the late 13th century. He was at Norham in 1292, probably in the camp of Robert de Brus, then Earl of Carrick.
He was married to Helen (sometimes called Ellen), who herself had previously been married to Mormaer Maol Choluim II, Earl of Fife. By Helen, he had three sons, including his successor Gartnait, and two daughters. His daughter Isabella of Mar was the first wife of Robert I of Scotland and mother of Marjorie Bruce.
The last record of a living Domhnall comes from 1297, and the earliest record of his son Gartnait as Mormaer is from 1305, creating the range of Domhnall's possible year of death to somewhere in between these two points. However, a document dating to 1302,[1] containing terms of reconciliation between Edward I and Robert, stipulates that Robert should act as warden of Gartnait, implying that Domhnall had just died.
Links: Thepeerage: http://thepeerage.com/p10916.htm#i109156
Wikipedia: English: http://en.wikipedia.org/wiki/Domhnall_I,_Earl_of_Mar
Donald (Sir),6th Earl of Mar; knighted 1270; one of the leading Scottish nobles who recognised Alexander III's daughter Margaret as heir to the throne after her father's death Feb 1283/4; following Margaret's death 1290 supported Robert the Bruce but was one of the seven Earls of Scotland who referred a decision in the matter to Edward I of England, to whom he swore fealty as overlord 13 June 1291; nevertheless was a leading participant in the Scottish Uprising against the English shortly afterwards, being captured by them following the Battle of Dunbar 27 April 1296 and renewing his allegiance to Edward I thereafter. [Burke's Peerage] Donald, Earl of Mar, by his 1st wife Helen, daughter of Llewellyn ap Iorwerth, Prince of Wales. [Magna Charta Sureties, Line 41-5] Donald, Earl of Mar, by Helen or Elen, illegitimate daughter of Llewellyn ap Iorwerth, Prince of Wales, widow of Malcolm, Earl of Fife. [Magna Charta Sureties, Line 41b-5] Donald, Earl of Mar, was knighted 1270, living 25 July 1297, d. shortly thereafter. His wife, and mother of Isabel, was Helen, widow of Malcolm, 7th Earl of Fife, d. 1266, and daughter of Llewellyn, Prince of North Wales. [Ancestral Roots, Line 252-30]
Earl Domhnall mac Uilleim (Donald of Mar) 6th Earl of Mar DD | ||||||||||||||||||||||||||||||||||
Elen (Helen) ferch Llywelyn | ||||||||||||||||||||||||||||||||||
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