The son and heir of John Fitzalan, Lord of Oswestry and Clun, from Shropshire.
After the death of his mother's brother Hugh d'Aubigny, 5th Earl of Arundel, and without direct heirs, he inherited jure matris the castle and honour of Arundel in 1243, which, according to the admission of 1433, he was held to have become de jure Earl of Arundel [REF].