He was a half brother of Henry III of England; his mother was Isabella of Angouleme, the second wife of King John, his father was Hugh X of Lusignan, the count of La Marche, whom Isabelle married in 1220.
Aymer was illiterate, ignorant of the English language, and wholly secular in his mode of life.
Aymer, however, gained, the support of the pope; he was on his way back to England when he was overtaken by a fatal illness at Paris.