Both of them...

Paddy has broken his leg and his buddy Mike comes over to see him.

Mike says, "How you doin'?"

"Paddy says, "Okay, but do me a favor, run upstairs and get me my slippers, my feet are freezing."

Mike goes upstairs and sees Paddy'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, "No way! Prove it."
Mike shouts downstairs, "Paddy, both of em?"

Paddy shouts back, "Of course both of em, what's the point of taking just one?"