In 1120 Robert was declared of age and inherited most of his father's lands in England, while his twin brother took the French lands. However, in 1121, royal favour brought Robert the great Norman honors of Breteuil and Pacy-sur-Eure, with his marriage to Amice de Gael, daughter of a Breton intruder the king had forced on the honor after the forfeiture of the Breteuil family in 1119. Robert spent a good deal of his time and resources over the next decade integrating the troublesome and independent barons of Breteuil into the greater complex of his estates. He did not join in his brother's great Norman rebellion against King Henry I in 1123–24. He appears fitfully at the royal court despite his brother's imprisonment until 1129. Thereafter the twins were frequently to be found together at Henry I's court.