"My aunt Minnie said that he lived to be old and died in Texas."

While a number of guerrillas ended up in Texas after the war, Anderson was not among them, I'm afraid. Anderson was killed in Missouri in 1864 just after the massacre at Centralia, toward the end of Price's Raid. He was 25 at the time of his death and was married, though I do not recall if he had any kids.

Albert Castel has an excellent book on him titled "Bloody Bill Anderson: The Short, Savage Life of a Civil War Guerrilla." It's a fantastic if short biography of the man.