Robert the younger took part in several of the military campaigns of Edward I, Edward II and Edward III in Wales, Scotland and France. His coat of arms appears in the 1298 Falkirk Roll at the Battle of Falkirk. He was married to Margaret Mortimer, daughter of Roger Mortimer, 1st Baron Wigmore. He also officiated at the Coronation of Queen Isabella, wife of Edward II, in 1308. His only son Thomas died before him, and when Robert died in 1331, he was succeeded by his nephew John de Vere, 7th Earl of Oxford.