1911 Encyclopædia Britannica (1911)
“ Strongbow having died without male issue, His daughter Isabel became countess of Pembroke in her own right, and the title was borne by her husband, Sir William Marshal, or Le Maréchal, second son of John le Maréchal, by Sibylle, the sister of Patrick, earl of Salisbury. John le Maréchal was a partisan of the empress Matilda, and died about 1164. ”
