Twins having sex with each other in reality is not hot. It seems like a good idea while you're imagining it but put into practice it would put you off...well it would put me off anyway. If you had a sibling you'd understand. I have a sister I don't find the idea of sex with her attractive at all. I feel disgusted even typing that. The idea of picking up a couch and throwing it at my sister still brings back fond memories though. Now we're friends.
If I was to do twins they could talk to each other and just act like sisters and that would hot enough. They could do that thing where one takes you in hand and sticks you into her sister but that would be the limit of their sexual contact.
