'Game of Thrones' Star Whew! Thank God ... My Sister Didn't Play My Sister

6/14/2014 12:02 AM PDT

Alfie Allen, best known as Theon Grayjoy on "Game of Thrones," came thiiis close to trying to bone his real life sister, singer Lily Allen -- but wait, wait ... don't freak out!

See, Lily almost played Alfie's sister on the show -- which would've been seriously awkward since he tries to grope his TV sis before he knows they're bro and sis. Yeah, GoT is confusing. And awesome.