Who is Dr. Thomas Stone from Cutting for Stone and what is their importance?

Dr. Thomas Stone meets Sister Mary Praise on a ship bound for Africa and impregnates her at Missing Hospital seven years later. When Sister Mary Praise dies in childbirth, Dr. Stone leaves Africa because he is unable to recover from his grief. He abandons his boys, moves to New York City, and goes onto become a renowned liver surgeon. He later reunites with his sons.