Isabel de Avenel was born about 1143 in Sandhurst, Tewkesbury Borough, Gloucestershire, England to Robert Aveernal, Jusiciar of Lothian and Sibyl. She was mistress to William I, King of Scotland and had at least children by him.
Isabel MacWilliam
Ada, wife of Patrick I, Earl of Dunbar
Anfrica, wife of William de Say
She died about 1235 in Stirling, Scotland. It is unknown what happened to her body.