Complex sentence: In 1377, Pierre d'Alençon inherited his brother Robert's county of Perche and with it the castle of Bellême and the service of the Carrouges father and son as well as that of Le Gris.
Split into simpler sentences: In 1377, Pierre d'Alençon inherited his brother Robert's county of Perche and with it the castle of Bellême. In addition, he gained the fealty of his brother's vassals, including the Carrouges father and son as well as Jacques Le Gris.