William I de Ros , Mp, Lord of Roos
William I de was born about 1196 in Helmsley Castle, North Ride, Yorkshire, England.  He died in 1264 in Poitou, France.¹ 

 Lucy FitzPiers
Lucy was born about 1214 in Brecknock, Wales.  She died after 1266.² 

 Robert IV "1st Baron" de Ros , of Belvoir, Mp
Robert IV "1st Baron" de was born in 1233 in Helmsley Castle, North Ride, Yorkshire, England.  He died at the age of 52 on May 17th, 1285 in Belvoir Castle, Leicestershire, England.³