Complex sentence: Simeon Baldwin Chittenden married Mary Elizabeth Hartwell, the daughter of Sherman Hartwell and Sophia Todd; who was the nephew of American founding father Roger Sherman and his first wife Elizabeth Hartwell.
Split into simpler sentences: Simeon Baldwin Chittenden married Mary Elizabeth Hartwell, the daughter of Sherman Hartwell and Sophia Todd. Her father was the nephew of American founding father Roger Sherman and his first wife Elizabeth Hartwell.