Joan of Cornwall, heiress of Modbury

Joan of Cornwall was the daughter of Richard Plantgenet, Earl of Cornwall and Joan de Valletort. However, she was the legal daughter of Joan de Valletort's husband, Alexander Okeston. Joan of Cornwall was not related by blood to Alexander Okeston.

Joan of Cornwall, (alias Joan Okeston, legally the daughter and heiress of Sir Alexander Okeston of Modbury, Devon)[19] who in 1283 received a grant from her half-brother Edmund, 2nd Earl of Cornwall (d.1300) in which she was called "sister".[20] Modbury was part of the Valletorts' feudal barony of Harberton and was granted to Sir Alexander Okeston, following his marriage to the Earl of Cornwall's mistress, Joan, widow of Ralph de Valletort, by Roger de Valletort, Ralph's brother.[21] She married twice, firstly to Richard de Champernowne (2nd son of Sir Henry Champernowne of Clyst Champernowne, Devon), by whom she had a son, Sir Richard de Champernowne, and secondly, Sir Peter de Fishacre, of Combe Fishacre and Coleton Fishacre, Devon,[22] by whom she had no issue. Following the death of her childless brother Sir James Okeston, the manor of Modbury was conveyed by order of Edward II (1307–27, great-nephew of Richard, Earl of Cornwall), to his sister's grand-son Sir Richard de Champernowne.[23]

[Citation Required]

http://en.wikipedia.org/wiki/Richard,_1st_Earl_of_Cornwall

Richard had several documented out-of-wedlock children. One of Richard's mistresses was Joan de Vautort, widow of Ralph de Vautort[17] (d. 1267), feudal baron of Harberton, Devon[18] and Trematon, Cornwall. Joan later married Sir Alexander Okeston, lord of the manor of Modbury in Devon, a part of the Vautorts' feudal barony of Harberton that had been granted him by Roger de Vautort.[17] Joan bore Alexander a son and heir, Sir James Okeston.[19]

By Joan de Vautort or other mistresses, the Earl of Cornwall had at least three sons and a daughter as follows:[20]

Joan of Cornwall, daughter of Joan de Vautort, in 1283 received a grant from her half-brother Edmund, 2nd Earl of Cornwall, in which she was called "sister".[23][24] The younger Joan married (1st) Richard de Champernoun and (2nd) Sir Peter de Fishacre of Combe Fishacre and Coleton Fishacre, Devon,[25] having no issue by the second. Her childless half-brother Sir James Okeston made her son (or grandson) Richard de Champernoun his heir.[23][24]

Source: 19. Vivian, Lt.Col. J.L., (Ed.) The Visitations of the County of Devon: Comprising the Heralds' Visitations of 1531, 1564 & 1620, Exeter, 1895, p. 160, pedigree of Champernowne