Complex sentence: Realizing Cynthia had forgotten most of her English and would be unhappy if separated from the life she knew, some Rangers urged Ross to let her return to the Comanches, but he felt it best to try to return her to her birth family.
Split into simpler sentences: Realizing Cynthia had forgotten most of her English and would be unhappy if separated from the life she knew, some Rangers urged Ross to let her return to the Comanches. However, he felt it best to try to return her to her birth family.