Have done lots of research..the thomas morieux who married blanche plantagenet, illagitamet daughter of john of gaunt and marie st. Hillaire, was the sister of the elizabeth morieux i am searching for. Their father was sir john morieux (knight) born 1308. Thomas and blanche did not have any children. I found this infor in cambridge uni history page. Elizabeth married edmund fitz lucas in 1360 and had a son son john. I am trying to find who elizabeth and thomas mother was