25 years might be enough. I dated twins consecutively as after dating one, I discovered I really liked her sister a lot better (same looks, much better personality). But twin# 1 eventually admitted to being a bit miffed at being dumped for her sister (we look the same so why do you like HER so much better) and twin #2 was supportive and chose her over me (imagine that) so the whole thing fell apart. I should have waited until twin # 1 found someone else. In 25 years it could have happened.
With all the mention about manifolds, I am pretty sure they are talking about conjoined twins. I have never had much attraction to those and prefer my twins to be totally independent.
