He married Sibyl Marshall. He also married Margaret de Quinci, daughter of Roger de Quency, 2nd Earl of Winchester and Helen de Galloway, in 1238.
Children of William de Ferrers and Sibyl Marshall
* Isabel Ferrers
* Maud Ferrers
* Agnes Ferrers+
* Eleanor Ferrers
* Agnes de Ferrers
* Sibyl de Ferrers+ b. b 1231
* Joan de Ferrers+ b. b 1242
* William de Ferrers+ b. b 1254, d. 1288
* Agatha Ferrers b. b 1254
Children of William de Ferrers and Margaret de Quinci
* Robert de Ferrers, 6th Earl of Derby+ b. c 1239, d. c 1279
* Joan de Ferrers+ b. b 1252, d. 19 Mar 1309/10
William de Ferrers, 5th Earl of Derby 
