Here is one of 16 ways to trace Elizabeth Willoughby back to Roderigo Diaz de Bibar, known as "El Cid.":
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 = Joan Bourchier d. 1470
5. Sir John Bourchier, Baron Berners d. 1474 = Margery Berners
6. William Bourchier, Cout of Eu = Anne of Gloucester 1383-1438
7. Thomas of Woodstock, Duke of Gloucester 1354/5-1397 = Eleanor de Bohun
8. Edward III, King of England 1312-1377 = Philippa of Hainaut
9. Edward II, King of England 1284-1327 = Isabella of France
10. Edward I, King of England = Eleanor of Castile 1241-1290
11. Fernando III, King of Castile 1191-1252 = Jeanne de Dammartin
12. Alphonso IX, King of Leon = Berengaria of Castile d. 1244
13. Alphonso VIII, King of Castile 1155-1214 = Eleanor of Domfront
14. Sancho III, King of Castile = Blanche of Navarre d. 1158
15. Garcia VII, King of Navarre d. 1150 = Marguerite de l'Aisle
16. Ramiro II Sanchez of Navarre, Lord of Urroz = Christina Diaz
17. Roderigo Diaz de Bibar "El Cid" ca. 1043-1099 = Ximena Diaz