Magazine editor and columnist and NYT bestselling author Cat Marnell posted on Twitter that Ryan Reynolds and Blake Lively had an affair with each other while he was still married to Scarlett Johansson and she was dating Penn Badgley. She says that she was told this by a beauty editor and that Us Magazine was going to publish it until Ryan and Blake's teams got involved and squashed the story.
Ryan and Blake starred together in "The Green Lantern" which filmed from March to August 2010 in Louisiana. Blake was dating Penn until November 2010. Ryan was with Scarlett until December 2010. Ryan and Blake didn't officially become a couple until sometime in late 2011.
Cat deleted the tweet but the internet is forever.
There were rumors at the time of cheating with one source telling the National Enquirer that Scarlett was “incredibly bitter about it. In a way, Scarlett feels like Blake actually stole Ryan Reynolds from her because it was when he started shooting Green Lantern with Blake in 2010 that everything fell apart.”
Ryan and Blake pictured together in summer 2010 at ComicCon
Sources:
1 2 and my screenshot