Sometime between 2261 and 2267, he was stationed at a lonely outpost at Aldebaran III, where he met his future wife, Janet. Though he was 26 years older than her, he fell in love with her and they married.
Later, they worked together on trying various carbohydrate compounds to slow down the degeneration of plant life. Wallace died sometime prior to 2267; he was described by his wife as a 'brilliant' and 'great' man, whom she admired. At the time of her marriage to Theodore, she believed herself to be over James T. Kirk, but she was wrong. (TOS: "The Deadly Years")