Complex sentence: Power Y Giralt was amongst the delegates who proposed that slavery be abolished in Puerto Rico, and he sent a letter to his mother, Josefa Giralt, suggesting that if the proposals were approved, she should be the first one to grant her slaves their freedom.
Split into simpler sentences: Power Y Giralt was amongst the delegates who proposed that slavery be abolished in Puerto Rico. He sent a letter to his mother, Josefa Giralt, suggesting that if the proposals were approved, she should be the first one to grant her slaves their freedom.