Alice Comyn, his niece and heir, married Henry Beaumont, a French nobleman in the English service. Beaumont was to claim the earldom of Buchan in right of his wife, a claim pursued with such relentless determination that it was a major factor in bringing about the Second War of Scottish Independence in the 1330s and beginning anew the war between the Comyns and the Bruces.
Henry de Beaumont, jure uxoris 4th Earl of Buchan and suo jure 1st Baron Beaumont (died 10 March 1340) was a key figure in the Anglo-Scots wars of the thirteenth and fourteenth centuries, known as the Wars of Scottish Independence.
Henry de Beaumont was a veteran campaigner who participated in every major engagement, from the Battle of Falkirk in 1298 to the Battle of Halidon Hill in 1333. Although not now a widely known figure, he was, nevertheless, of considerable military and political importance. His long experience of the Scottish wars led him to develop a battle technique later used to great effect at Crécy and Agincourt. As one of a group of Anglo-Scots nobles known as the 'disinherited' — those who had fought against King Robert Bruce — he was to do much to overturn the peace between England and Scotland established by the Treaty of Northampton and bring about a Second War of Scottish Independence. By his marriage shortly before 14 July 1310 to Alice Comyn, Countess of Buchan (died 3 July 1349), the niece and heir of John Comyn, Earl of Buchan, he was recognised as Earl in right of his wife.