Trevor Williams was a descendant of a marriage in 1300 between Howel Gam ap David of Penrhos Castle and Joyce, a daughter of the Herefordshire based Scudamore family. Roger Williams, Trevor's grandfather and High Sheriff of Monmouthshire, acquired Llangibby Castle in 1545National Library of Wales - Llangibby castle and adopted the surname Williams (derived from his father's name, William) in 1562. His son, Charles, who became M.P. for Monmouthshire and was knighted in 1621, also became Sheriff of Monmouthshire in 1627. Sir Charles, Trevor's father, was a noted Puritan who presented a fine Jacobean pulpit with the text "Woe Be to Me if I Preach not the Gospel" to Caerwent church in 1632.Jeremy Knight, Civil War and Restoration in Monmouthshire, 2005, He died in 1642.
