Eleanor was the youngest child of Simon de Montfort, 6th Earl of Leicester and Eleanor of England. She had five older brothers:
Henry de Montfort,
Simon de Montfort the Younger,
Amaury de Montfort,
Guy de Montfort and Richard de Montfort. Her place of birth is unknown. Eleanor's maternal grandparents were
John, King of England and his
Queen consort,
Isabella of Angoulême. Her maternal uncles included King Henry III of England, and the King of the Romans,
Richard of Cornwall. Her maternal aunts included the Queen of Scotland,
Joan of England; the Holy Roman Empress, Queen of Germany and Queen of Sicily,
Isabella of England; and the wife of the Prince of Wales,
Joan, Lady of Wales. When Eleanor was thirteen years old, her father Simon de Montfort, and brother Lord Henry were killed at the
Battle of Evesham (4 August 1265). According to the chroniclers,
Nicholas Trivet,
William Rishanger and others, Earl Simon had earlier made an alliance with
Llywelyn ap Gruffudd, whereby it was agreed that Llywelyn and Eleanor would marry. After Earl Simon's death, his family was forced to flee the
Kingdom of England: Countess Eleanor took her daughter to the safety of the Dominican nunnery at
Montargis, France, a Montfort foundation. ==Marriage to Llywelyn ap Gruffydd==