The FitzWarin family took its name from Guarine (or Warin) de Meez, said to have been a member of the House of Lorraine who came to England after the Norman Conquest.

His father, Fulk (IV) FitzWarin, was appointed by King Richard I to defend the Welsh Marches, later rebelled against (and was outlawed by) King John, and, having made his peace with King Henry III, drowned in a river during the Battle of Lewes in royal service during the Second Barons' War.

When FitzWarin married Gruffydd's daughter, the latter restored the manor to his new son-in-law.

[1] FitzWarin continued to serve the crown, fighting in the Scottish Wars and in Flanders.

[1] FitzWarin married Margaret, daughter of Gruffydd ap Gwenwynwyn, Prince of Powys Wenwynwyn.