Isabelle de Conde was born circa 1214 to Jacques de Condé (c1195-c1258) and Agnes de Rœulx (c1215-aft1247) .
Children
| Name | Birth | Death | Joined with |
| Reginald de Fiennes (c1232-aft1270) | |||
| Robert de Fiennes (c1233-) | |||
| Enguerrand de Fiennes (c1235-) | |||
| William II de Fiennes (c1245-1302) | 1245 | 11 July 1302 | Blanche de Brienne (c1252-c1302) |
| Giles de Fiennes (c1251-) | |||
| Maud de Fiennes (c1254-c1298) | 1246 | 6 November 1298 | Humphrey de Bohun, 3rd Earl of Hereford (c1249-1298) |