Tom Horton, the eldest son of Tom and Alice, was born in 1931 along with his twin sister Addie Horton. His other siblings include Mickey, Bill, and Marie Horton. Tommy Jr. originally married a woman named Kitty and had a daughter Sandy, but he was believed to have been killed in Korea in 1953.

In 1967, Tommy Jr. returned to Salem with Bill Horton. Tommy believed his name to be Dr. Mark Brooks and was a veteran from the Korean War. He had no memory to his prior life and had undergone plastic surgery to reconstruct his disfigured face. Mark helped Bill through therapy with his hand and encouraged him to return to his career as a surgeon. Upon arriving in Salem as Dr. Mark Brooks, Tommy got a position practicing medicine at Salem University Hospital where Marie became his research assistant, and the two fell in love. Mark's presence in Salem affected the Horton's greatly, and Tom and Alice began to notice his similarities to Tommy Jr. When Tom Sr. and Mickey investigated they did in fact find proof that Mark Brooks was Tommy Jr. Tom had suffered cruelly as a POW in Korea, and after escaping and saving the life of a Soviet soldier Tommy Jr.'s face was reconstructed as a reward.

With his identity revealed Mark had to admit who he was, and that he was in love with his sister. Tommy and Marie broke off their relationship, and Marie was so devastated she ran off and became a nun. Tommy would then come to know his daughter Sandy, and try to work out things with his wife Kitty. However, Kitty continued to lust after Dr. Elliot Kincaid, and after hiring a private detective Tommy confronted Kitty at Elliot's apartment. Kitty used her heart condition and faked chest pains to get out of the bind she was in. She was taken to the hospital, but checked out fine. Later upon learning Kitty had numerous affairs in the past Tommy could no longer trust Kitty and he divorced her in 1969.

In 1977 Tommy began to date Linda Patterson and eventually proposed marriage. Linda accepted, but later broke off the engagement to marry Bob Anderson, who had just promoted her to head of his company. In 1979, Tommy left Salem. Sometime later (during the early ‘80s), Alice mentioned he was living in Hawaii, but no one appears to have heard from or spoken of Tommy since.