 Lancaster was married to Isabella , daughter of Henry , Lord Beaumont , in 1330 . The two had no sons , but two daughters : Maud and Blanche . While Maud was married to William I , Duke of <unk> , Blanche married Edward III 's son John of Gaunt . Gaunt ended up <unk> Lancaster 's possessions and <unk> title , but it was not until <unk> , when the dying King Edward III was largely incapacitated , that he was able to restore the palatinate rights for the county of Lancaster . When Gaunt 's son Henry of <unk> <unk> the crown in <unk> and became Henry IV , the vast Lancaster inheritance , including the Lordship of <unk> , was merged with the crown as the Duchy of Lancaster . 
