Complex sentence: After her death, Henry would take care of them and eventually raise them the peerage, in turn they gave him unwavering loyalty and fought and promoted his and his Lancastrian family's interests to the best of their ability.
Split into simpler sentences: After her death, Henry would take care of them and eventually raise them to the peerage. In turn they gave him unwavering loyalty and fought and promoted his and his Lancastrian family's interests to the best of their ability.