William de Ferrers, 4th Earl of Derby was born circa 1168 to William de Ferrers, 3rd Earl of Derby (-1190) and Sibylla de Braose (-1227) and died circa 1247 of unspecified causes. He married Agnes de Kevelioch (c1174-1247) .
|Offspring of William Ferrers and Agnes de Kevelioch (c1174-1247)|
|William de Ferrers, 5th Earl of Derby (c1193-1254)||1193||28 March 1254||Sibyl Marshall (1209-bef1238) Sibyl Marshall (1209-bef1238) Margaret de Quincy (c1218-bef1285)|
|Bertha de Ferrers (1218-1267)||1218 Thetford, Norfolk, England, United Kingdom||10 February 1267 England, United Kingdom||Thomas de Furnival (1200-1238) Thomas de Furnival (1200-1238) Ralph Bigod (c1215-1260)|
|Sibyl de Ferrers (1216-?)|
|Thomas de Ferrers|
|Hugh de Ferrers|