Both Reeves and Culver have long been dead, Culver died of AIDS in 1987 while the Hollywood heartthrob died in 2004 of heart failure, but the new claims have grabbed headlines.
In new book 'Hollywood Babylon Strikes Again', Culver gives details of their relationship in an interview conducted before his death in 1987, reported Daily Mail online.
The porn star alleges that he met Reeve when they were both auditioning for a Broadway role in the late-1970s.
"Christopher was a great lover and I think I liberated him sexually. I didn't think he was gay but he seemed willing to try anything once. He was curious," says Culver.
The news may come as a surprise to the millions of Reeve fans who saw the star enjoy a healthy 12-year marriage to wife Dana.
He also had a son William with Dana, as well as children Matthew and Alexandra from a previous relationship.
While Reeve is perhaps best known for his role as the macho superhero Superman, he also took on a role in 1982 film 'Deathtrap', which saw him share a kiss with co-star Michael Caine.
Reeve died in 2004, nearly a decade after he was paralysed in a horse riding accident.
Reeve was paralysed from the shoulders down when he fell from a horse in 1995. The accident turned him into a worldwide advocate for spinal cord research.