Found posted in a humor newsgroup (rec.humor.funny)
A friend of mine gets peeved when passers-by pat his twin three-year-olds on
the head and ask, 'Are they twins?' But he has found what he considers the
perfect reply. 'No, they're not,' he says. 'I've got two wives'.
Tom's note: I have twin sons (they are adults now) and I noticed that when
they were toddlers, most people would ask, "Are they twins?" Here's two little
boys, same size, dressed alike and being transported in identical strollers.
What would you think? Actually, the only people who noticed that they were
twins were the people who had twins themselves.