Mary and her elder sister, Eleanor de Bohun, were the heiresses of their father's substantial possessions. Eleanor became the wife of Thomas of Woodstock, 1st Duke of Gloucester, the youngest child of Edward III. In an effort to keep the inheritance for himself and his wife, Thomas of Woodstock pressured the child Mary into becoming a nun. In a plot with John of Gaunt, Mary's aunt took her from Thomas' castle at Pleshey back to Arundel whereupon she was married to Henry Bolingbroke, the future Henry IV.
Marriage and children
Mary married Henry—then known as Bolingbroke—on 27 July 1380, at Arundel Castle. 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. Her second child, Thomas, was born probably at London shortly before 25 November 1387.
^According to some sources, in 1382 she had a son who died shortly after birth. This is incorrect, as it's based on a misreading of a contemporary account book, by J.H. Wylie, in his biography of Henry IV (published in the 19th century). Wylie missed a line which made clear that the boy in question was Mary's nephew, Humphrey, 2nd Earl of Buckingham. There is no evidence that there was any child born to her at this time (when Mary de Bohun was only about 14).