Complex sentence: Cora Semmes was the daughter of Raphael Semmes (1786--1846) and Mary Matilda (Jenkins) Semmes (1800--1881), who was the sister of Confederate Senator Thomas Jenkins Semmes.
Split into simpler sentences: Cora Semmes was the daughter of Raphael Semmes (1786--1846) and Mary Matilda (Jenkins) Semmes (1800--1881). She was the sister of Confederate Senator Thomas Jenkins Semmes.