Euphemia was a daughter of Hugh, Earl of Ross, and Margaret de Graham, Hugh's second wife and daughter of Sir John de Graham of Abercorn.

It appears that there was an obstacle of affinity to this second marriage, and a papal dispensation by Pope Innocent VI was required for it to be recognized by the Catholic Church.

The affinity was due to her first husband, John Randolph, Earl of Moray, having been a second cousin of Robert Stewart.

[2] The children of Robert's first marriage to Elizabeth Mure were considered illegitimate by some due to reasons of consanguinity.

Both sets of children from each marriage considered themselves rightful heirs to the throne, which constituted considerable future conflict.