The son of Gilbert fitz Gilbert de Clare, Earl of Pembroke, was Richard de Clare, 2nd Earl of Pembroke (died 1176), known as Strongbow, a leader of the Norman invasion of Ireland. His only son died while still a minor, and Strongbow's many Irish and Welsh possessions passed with his daughter Isabel, to her husband, William Marshal. Some of these lands would be brought back into the family via the marriage of one of the coheiresses of Isabel de Clare and William Marshal, Isabel Marshal, to her distant cousin, Gilbert de Clare, 4th Earl of Hertford (died 1230). He also inherited from his mother the estates of his maternal grandfather, William Fitz Robert, 2nd Earl of Gloucester (died 1183), including the earldom and honour of Gloucester and the lordship of Glamorgan.