If this is indeed true, which would make you most luckiest son of a bitch on Earth if these chicks are good looking, here's what you do.
1. You do the chick you've known the longest. She gets your virginity. You tell her to shut her damn mouth if she happens to know the twins because you want this to be a secret between the two of you.
2. Don't let the twins know you're not a virgin anymore. Figure out which of the twins is freakier. Get the idea into her head that you want the threesome but you want her more than the other sister. If she succeeds in getting it to happen you've fucked all three chicks. If she doesn't, you fucked two out of three and that ain't half bad.
3. Don't become any of those chicks' intellectual whore. If you're not hitting it, then you're quitting it.