| Father | Edmund Deincourt 1st Baron Deincourt, 8th Lord Eyncourt and MP (1245 - 1327) |
| Mother | Isabel de Mohun (1243 - 1280) |
| Sibling | Baroness Matilda Deincourt (1268 - 1324) |
| Sibling | Margaret Deincourt (1275 - 1333) |
| Sibling | Isabel Deincourt (1275 - 1325) |
| Sibling | Johanna Deincourt (1275 - ) |
| Sibling | William Deincourt (1273 - 1314) |
| Sibling | Edmund Deincourt (1270 - 1314) |
| Sibling | Isabel Deincourt (1268 - 1348) |
| Sibling | Isabel Deincourt (1280 - 1347) |
| Sibling | John Deincourt Master of Blankney (1265 - 1326) |
| Sibling | Edmund Deincourt ( - ) |