Mary was the daughter of Humphrey de Bohun, 7th Earl of Hereford, and Joan FitzAlan (1347/48–1419), the daughter of Richard FitzAlan, 10th Earl of Arundel, and Eleanor of Lancaster. Through her mother, Mary was descended from Llywelyn the Great.
Eleanor became the wife of Thomas of Woodstock, 1st Duke of Gloucester, the youngest child of Edward III. John of Gaunt had planned for the marriage between Mary and Henry to remain unconsummated until Mary was sixteen but the couple disobeyed. Consequently, Mary became pregnant at fourteen. The firstborn child lived only a few days.
She was buried at the Church of Street Mary de Castro, Leicester.
