Robert FitzStephen was a Cambro-Norman soldier, one of the leaders of the Norman invasion of Ireland, for which he was granted extensive lands in Ireland. He was a son of the famous Nest, daughter of Rhys ap Tewdwr, the last king of Deheubarth. His father was Nest's second husband, Stephen, Constable of Cardigan. Following the death of her first husband, Gerald de Windsor, her sons had married her to Stephen, her husband's constable for Cardigan. By Stephen, she had another son, possibly two; the eldest was Robert, and the younger may have been Hywel.

The Anglo-Norman invasion of Ireland took place during the late 12th century, when Anglo-Normans gradually conquered and acquired large swathes of land from the Irish, over which the kings of England then claimed sovereignty, all allegedly sanctioned by the papal bull Laudabiliter. At the time, Gaelic Ireland was made up of several kingdoms, with a High King claiming lordship over most of the other kings. The Anglo-Norman invasion was a watershed in Ireland's history, marking the beginning of more than 800 years of direct English and, later, British, conquest and colonialism in Ireland.