Gwladus ferch Llywelyn was born on an unknown date to Llywelyn ab Iorwerth (c1173-1240) and Joan of England (1190-1236) and died 1251 of unspecified causes. She married Reginald de Braose, 9th Baron Abergavenny (1178-1228) 1215 JL . She married Ralph de Mortimer (bef1198-1246) 1230 JL .
Sources differ as to whether Gwladus was Llywelyn's legitimate daughter by his wife Joan or an illegitimate daughter by Tangwystl Goch. Some sources say that Joan gave her lands to Gwladus, which suggests, but does not prove, the former. Gwladus is recorded in Brut y Tywysogion as having died at Windsor in 1251.
Children
| Name | Birth | Death | Joined with |
| Roger Mortimer, 1st Baron Mortimer of Wigmore (1231-1282) | 1231 | 30 October 1282 | Maud de Braose (1224-1300) |
| Hugh de Mortimer | 26 February 1181 | Matilda le Meschin (-aft1189) | |
| John de Mortimer | |||
| Peter de Mortimer | |||
Footnotes (including sources)
| ‡ General |