Complex sentence: Dr. J.M. Stemmons never bought or sold slaves and was known to have retained his family inherited slaves simply for their very own safety, and he was a slave owner who supported the abolition of slavery in the United States.
Split into simpler sentences: Dr. J.M. Stemmons never bought or sold slaves and was known to have retained his family inherited slaves simply for their very own safety. He supported the abolition of slavery in the United States.