She was the wife of William de Cantilupe who, as a result of his marriage, acquired significant land holdings in both England and Wales.

William was the last of the Braose Marcher lords who possessed extensive lands in Wales, Herefordshire, Sussex and Devon.

William de Braose was hanged by Llywelyn the Great, Prince of Gwynedd in 1230 and the four young sisters became co-heiresses of valuable property.

[3] The couple later gained more lands in south west England and Wales through her mother's Marshal inheritance.

The barony of Abergavenny descended through Joan to the Hastings family while Totnes and the Cantilupe estates became possessions of Millicent's de la Zouche heirs.