| Father | William 2nd de Fiennes Baron de Tingry, Count de Fiennes & Lord of Wendover (1215 - ) |
| Mother | Blanche de Brienne Lady Loupeland (1245 - ) |
| Sibling | Lady Margaret Eleanor de Fiennes ( - ) |
| Sibling | Jean 1st de Fiennes Baron de Tingry and Fiennes ( - 1333) |
| Sibling | Joanna de Fiennes ( - ) |
| Sibling | Robert de Fiennes (1273 - ) |
| Sibling | Alice de Fiennes (1276 - ) |
| Sibling | John de Fiennes (1278 - 1324) |
| Sibling | Robert de Fiennes (1273 - 1274) |
| Sibling | Yolande de Fiennes (1275 - 1323) |
| Sibling | Baldwyn de Fienes ( - ) |
| Sibling | Isabeau Fiennes (1272 - 1360) |
| Sibling | John de Fiennes (1270 - 1335) |
| Sibling | Lady Margaret de Fiennes (1270 - 1333) |