A.J. was born and raised in Phoenix, Arizona, the son of actor Lorenzo Lamas and Michelle Cathy Smith, and grandson of actors Fernando Lamas and Arlene Dahl. He lived with his mother after his parents divorce, growing up with two sisters -- his younger sister, Shayne, also acts. He also has four younger sisters on his father's side: Paton Ashbrook, and Alexandra, Victoria and Isabella Lamas.
After graduating high school, A.J. won a modeling competition that sent him to New York where he took part in the International Modeling and Talent Association competition in 2001, winning the cold-reading category and receiving an honorable mention as Young Adult Actor of the Year, as well as winning Model of the Year. When he's not acting or modeling, A.J. enjoys golfing, and has been rated as one of the top players in Arizona, and is also skilled in Tae Kwon Do.
A.J. was Mr. Golden Globe in 2003, and was featured in the video Decisions - Are You Ready to Make the Right Ones?