She was the wife of Raoul III, Sire de Fougères, by whom she had one daughter, Jeanne de Fougères, who became the heiress to her father"s seigneury. Isabelle was born in 1212, the youngest daughter of Amaury I, Sire de Craon and Jeanne des Roches (c1195-1128 September 1238).
She had a younger brother, Maurice IV, Sire de Craon (1213–1250), who married Isabelle de Lusignan, a half-sister of King Henry III of England by whom he had three children. She had an elder sister, Jeanne who was bethrothed to the three-year-old Arthur of Brittany in 1223. Arthur died that same year, and nothing further is known about Jeanne.
Isabelle"s paternal grandparents were Maurice II de Craon and Isabelle de Meulan.
Her maternal grandparents were Guillaume des Roches, Seneschal of Anjou and Marguerite de Sablé. Amaury died in 1226, when Isabelle was fourteen years old.
