|SOME NOTES ON MEDIEVAL ENGLISH GENEALOGY|
Volume 8, page 586:
At the death of John, Lord Mautravers, in 1364, the Barony of Mautravers fell, according to modern doctrine, into abeyance between his granddaughters and coheirs: (1) JOAN, aged 22, who m., 1stly, Sir John DE KEYNES, of Wilts, and, 2ndly, Sir Robert ROUS; (2) ELEANOR, aged 19, who, surviving her sister Joan, who d. s.p., became de jure BARONESS MAUTRAVERS.
Douglas Richardson, in June 2002, provided further information about Joan - that by her first marriage to Sir John de Keynes (d. 1366) she had two children, John and Wenthliana (who both died without issue in 1375), and that she remarried by 1376, when she was living, but was presumably dead by 1377 [citing G. Paget, An Official, Genealogical, and Heraldic Baronage of England ].