identical cousins
Two people who act like enemies and say they're nothing alike, while in reality are best friends and practically the same person.
"Oh my god, can you believe that Lenny and Ruth haven't killed each other yet? They must really hate each other!"
"Dude, are you dense? They're identical cousins....they get together on Saturday nights and sew every week. They're basically best friends."
"Dude, are you dense? They're identical cousins....they get together on Saturday nights and sew every week. They're basically best friends."