Grosmont 's uncle , Thomas of Lancaster , was the son and heir of Edward I 's brother Edmund Crouchback . Through his inheritance and a fortunate marriage , Thomas became the wealthiest peer in England , but constant quarrels with King Edward II led to his execution in 1322 . Having no heir , Thomas 's possessions and titles went to his younger brother Henry – Grosmont 's father . Earl Henry of Lancaster assented to the deposition of Edward II in 1327 , but did not long stay in favour with the regency of Queen Isabella and Roger Mortimer . When Edward III took personal control of the government in 1330 , relations with the Crown improved , but by this time the older Henry was already struggling with poor health and blindness .