It's pretty much clear with sex, even using a condom. What is not clear is why there are two big TV sets on the wall practically right next to each other. And what's more, they are mounted at different angles! By the way, the man can clearly see how much he enjoys his girlfriend. Although to be honest she looks like a plank!
What else are sisters for? They're just for my brother to practice on her, to relieve his tension. Then he could achieve something in life instead of hanging out in dubious companies. And the sister won't be shortchanged.