Here is one of two descents tracing Elizabeth Willoughby from Maud of Brittany, bastard daughter of King Henry I of England:
1. Elizabeth Willoughby 1512-1562 = Sir Fulke Grevill, knight
2. Edward Willoughby = Margaret Nevill b. 1494/5
3. Richard Nevill, Lord Latimer ca. 1458-1530 = Anne Stafford
4. Sir Henry Nevill d. 1469 = Joan Bourchier
5. George Nevill, Lord Latimer = Elizabeth Beauchamp ca. 1417-1480
6. Richard Beauchamp, Earl of Warwick 1381/2-1439 = Elizabeth Berkeley
7. Sir Thomas Beauchamp 1338/9-1401 = Margaret de Ferrers
8. Sir Thomas Beauchamp, Earl of Warwick = Katherine de Mortimer d. 1369
9. Sir Roger de Mortimer, Earl of Marche = Joan de Geneville 1285/6-1356
10. Sir Piers de Geneville = Jeanne de Lusignan d. 1322
11. Hugh XII de Lusignan d. 1270 = Jeanne de Fougeres
12. Hugh XI de Lusignan = Yolande de Dreux 1218-1272
13. Pierre de Dreux = Alix de Thours d. 1221
14. Gui de Thours, Count of Brittany = Constance of Brittany ca. 1162-1201
15. Conan IV, Count of Brittany d. 1171 = Margaret of Huntington
16. Alan II, Earl of Richmond = Bertha of Brittany d. bef. 1167
17. Conan III, Duke of Brittany = Maud
18. Henry Beauclerc, King of England 1068-1135 = unknown mistress