Luis Merlo was born on June 13, 1966, in Madrid. As a child, he frequently traveled with his parents, Carlos Larrañaga and María Luisa Merlo, who were also actors, and he became accustomed to see them on their theatrical tours, both performing and backstage, along with his three siblings: Amparo Larrañaga, Kako Larrañaga, and Pedro Larrañaga, who is married to the Actress Maribel Verdú.