William Crassus, or Le Gros (d.1219), was the son of Stephen Le Gros

Étienne le Gros

Stephen le Gros was the second son of Stephen of Aumale. He married his cousin, the eldest daughter of Roger de Mortimer, his mother's nephew. By her they had one son, William Crassus or 'le Gros'....

. William was from an Anglo-Norman baronial family long established in central Normandy. He inherited Sodbury

Chipping Sodbury

Chipping Sodbury is a market town in the county of South Gloucestershire, south-west England, founded in the 12th century by William Crassus . The villages of Old Sodbury and Little Sodbury are nearby...

 from his uncle, William le Gros, 1st Earl of Albemarle

William le Gros, 1st Earl of Albemarle

William le Gros was the Count of Aumale , Earl of York, and Lord of Holderness. He was the eldest son of Stephen, Count of Aumale, and his spouse, Hawise, daughter of Ralph de Mortimer of Wigmore....

, primo-genitus. He was granted a licence to hold fairs and markets in (what is now) Chipping Sodbury

Chipping Sodbury

Chipping Sodbury is a market town in the county of South Gloucestershire, south-west England, founded in the 12th century by William Crassus . The villages of Old Sodbury and Little Sodbury are nearby...

in 1217.

William was appointed Seneschal of Normandy in 1203 by King John of England. He was a noted kinsman and follower of the elder William Marshal, 1st Earl of Pembroke.

He married Margaret, daughter of Robert Fitz Warren. By Margaret he had at least one son, his namesake, William Crassus, or Le Gros.