Lorenzo was born on the 20th January 1958 in Los Angeles, son of Fernando Lamas and Arlene Dahl. He was raised in Pacific Palisades until the family moved to New York in 1968. He went to a private school, Admiral Farragut Academy, and graduated in 1975, after which he moved back to California. Encouraged by his father, he went to Tony Barr's Film Actors Workshop. He started his career in 1976 with a small TV role. He began learning martial arts (karate and taekwondo) in 1979, and now has three blackbelts.
Lorenzo divorced his first wife Victoria Hilbert in 1983. After his whirlwind marriage to Falcon Crest publicist, Michele Smith, he was left with two children, daughter Shayne and son Alvaro Joshua (known as AJ, he is now 17 and doing modelling work). On the 25th January 1985, he married his third wife Kathleen Kinmont, daughter of his Falcon Crest co-star Abby Dalton, at the Elvis chapel in Las Vegas. They were divorced in 1993, but continued to work together on Renegade.
Lorenzo married his fourth wife Shauna Sand on the 27th April 1996, at his mother's house. They have three daughters, Alexandra Lynne, born on the 22nd November 1997, Victoria, born 24th April 1999, and Isabella Lorenza, born 2nd February 2001. Lorenzo also has a son with another Falcon Crest co-star, Daphne Ashbrook, making a total of 6 kids - 4 girls, 2 boys.
December 2002, he and wife Shauna filed for divorce. Because Shauna hates men with bleached hair, of course, Lorenzo bleached his hair blonde.
Lorenzo also has a commercial pilot's licence - which comes in handy as he flies between Vancouver (where he films The Immortal) and LA (where he resides) each week.