 All Thomas's children predeceased him and he left his estates to his younger brother John Morgan (1670-1720), who sat as Member of Parliament for Monmouthshire and served as Lord-Lieutenant of Breconshire and Monmouthshire.John also succeeded to the estate of his uncle and namesake, John Morgan (d. 1715), High Sheriff of Monmouthshire in 1697 and Member of Parliament for Monmouth, a merchant who had amassed a great fortune in London.John's eldest son Sir William Morgan was Member of Parliament for Monmouthshire from 1722 to 1731.