He was raised in Lake Elsinore, California. Kerwin's father was an acting coach, who brought home scripts for his son to read. His mother was also a performer and later, a talent agent. He is the youngest of five brothers. His brother Shane was his stand-in. He has a daughter, Savanah Paige, with Kristen Lansdale and four children with his wife Yvonne: daughters Terah, Trinity and Kailani, and son Justus. He gave up acting in the mid-1990s and worked as a minister with U-Turn For Christ in Kaua'i, Hawaii."