Illegitimate children
Richard had several documented out-of-wedlock children. One of Richard's mistresses was Joan de Vautort, widow of Ralph de Vautort (d. 1267), feudal baron of Harberton, Devon 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. Joan bore Alexander a son and heir, Sir James Okeston.
By Joan de Vautort or other mistresses, the Earl of Cornwall had at least three sons and a daughter as follows:
Philip of Cornwall, a priest.
Sir Richard of Cornwall, who received a grant from his half-brother Edmund, 2nd Earl of Cornwall (d. 1300), in which he was called "brother". He married Joan, allegedly daughter of John Fitzalan III, and by her had three sons and a daughter. He was slain by an arrow at the Siege of Berwick in 1296. His daughter Joan of Cornwall married Sir John Howard, from whom the Howard family, Dukes of Norfolk, are descended.
Sir Walter of Cornwall, who received a grant of the royal manor of Brannel, Cornwall; from his half-brother Edmund, 2nd Earl of Cornwall, in which he was called "brother". He was ancestor of the Cornwalls of Branell.
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". The younger Joan married (1st) Richard de Champernoun and (2nd) Sir Peter de Fishacre of Combe Fishacre and Coleton Fishacre, Devon, having no issue by the second. Her childless half-brother Sir James Okeston made her son (or grandson) Richard de Champernoun his heir.