 That being said, Arnulf de Montgomery was likely created Earl of Pembroke by William Rufus, decades before Gilbert de Clare.Arnulf himself was rewarded by the king with lordship of Pembroke upon his family's construction of Pembroke Castle in the late 11th century.Like his father, Richard Fitz Gilbert de Clare (commonly known as Strongbow) was a supporter of Stephen, King of England - the last Norman king of England.