Randy has broken his leg and his buddy Mike comes over to see him. Mike says, "How you doin?" 

"Randy says, "Okay, but do me a favour mate, run upstairs and get me slippers, me feet are freezing."

Mike goes upstairs and sees Randy's gorgeous 19-year-old twin daughters lying on the bed.

He says, "Your dad's sent me up here to have sex with both of you."

They say, "Get away with ya.... prove it." 

Mike shouts downstairs, "Randy, both of em?"

Randy shouts back, "Of course both of em, what's the point of fuckin one?"