--- Michael Altschul, *A Baronial Family in Medieval England: The Clares,
1217-1314*, Baltimore MD (Johns Hopkins Press) 1965. p 37.
Earl Richard (Gilbert's father) arranged for the marriage of his son, then about ten years old, to Henry III's niece Alice, daughter of Hugh de Lusignan, count of La Marche & Angoulememe. Although she had two daughters, the match proved to be both a personal and a political failure; Gilbert and Alice were formally separated in 1271 and the marriage was finally annulled in 1285.
Even before the annulment, Earl Gilbert and King Edward I had discussed the
possibility of a marriage into the royal family.