Ryan Reynolds cheated on his wife Scarlett: Report

London: `Gossip Girl` star Blake Lively is reportedly the third person involved in the Scarlett Johannson-Ryan Reynolds split.

The actor who was recently voted `The Sexiest Man Alive` by People magazine had a fling with the 23-year-old on the sets of their film `Green Lantern`, reported E! Online.

Lively had broken up with her boyfriend of three years, Penn Badgley in October while shooting the superhero flick with the 34-year-old `The Proposal` star.

Johansson is currently holidaying with her friends in Jamaica and sources close to the actress say the marriage has been crumbling for months.

The 25-year-old began seeing a therapist in Manhattan two months ago to figure out her marital issues but was unable to "hash it out."

On the brink of the divorce announcement, Johansson rounded up three girlfriends last Saturday and flew down to an ultra exclusive resort in Port Antonio, Jamaica.