Mary and her elder sister, Eleanor de Bohun, were the heiresses of their father's substantial possessions.

[1] Eleanor became the wife of Thomas of Woodstock, 1st Duke of Gloucester, the youngest child of Edward III.

[1] In an effort to keep the entire inheritance for himself and his wife, Thomas of Woodstock pressured the child Mary into becoming a nun.

It was at Monmouth Castle, one of her husband's possessions, that Mary gave birth to her first child, the future Henry V, on 16 September 1386.

[5] Her children were:[b] Mary de Bohun died at Peterborough Castle, giving birth to her daughter Philippa.