Someone on Facebook that not only has the same name as you, they also look freakishly like you.
Usually the first result in Google when you search for your name.
Possible proof of a massive secret clone program that took place in the mid 80s.
Bloke 1: I added my Facebook twin as a friend last night, and now i'm sure some shady fuck in a suit is following me.
Bloke 2: Yeah, that's the Feds trying to cover up the massive clone program that took place in the 80s. You're fucked, dude!
Someone who looks like you or shares the same name on Facebook.
That girl looks just like you. She could be your facebook twin.
When someone sibling requests another person with the same birthday, only to realize that they would be twins.
Ben and Emily were listed as siblings on facebook, but then Ben remembered that they had the same birthday.
Ben-"Emily we are facebook twins!"
Emily-"OMG ur right!"