The MacDonnell claim to the Glens of Antrim dated from the marriage of Margery Byset, a daughter of the Mac Eoin, to John Mór MacDonnell, the second son of John of Islay, Lord of the Isles, in the 1390s. From the date of this marriage, or soon after, he and their descendants, the Clan MacDonald of Dunnyveg, considered the Lordship of the Glens to be theirs and styled themselves lords of Dunnyveg and the Glens, first found being styled so in a document dating to 1403. However the male line of the Bissetts was certainly far from extinct, and whatever gains made by the MacDonnells are uncertain. Bissett hostility to the MacDonnells may in fact have produced an alliance between the latter and the Savage family, and the war-making, on the side of the Ulster Gaels, against the English of Ulster, including the Savages, by a certain MacGion, likely the Mac Eoin Bissett, in 1403 may be associated with MacDonnell's new style as recognised by Henry IV. Also notable is that a member of the Savage family, the seneschal of Ulster Richard Savage, had the wardship of Margery, as well as her sister Elizabeth, following the late Mac Eoin's death, and this included some control over whatever for certain their actual inheritances may have been, but it is unknown what exactly this may have had to do with the marriage to MacDonnell or if any possible alliance may have been influential.