Who came from slave-owning family in the south to fight slavery in the north?

I am certain there were many individuals who would fit that description. One of the most notable ones would be General George H. Thomas, of Virginia. Thomas was a professional Army officer before the war, who unlike most of his fellow southerners elected to stay with the "old flag" and fight in the US Army against the Confederacy. His defense of Horseshoe Ridge after disaster struck at Chickamauga saved the Union Army there from complete rout and destruction, and earned him the nickname "The Rock of Chickmauga". Ironically, Thomas was never fully trusted by Union leaders, due to his southern birth. He went on to lead a crushing victory over the Rebel Army of Tennessee at Nashville in December, 1864. As a result of his decision to stay with the US Army he was estranged from his family for the rest of his life.