I have heard of people keeping 3 clowns together successfully but it can be a lot of fiddling around to make them get on. However, if you have a large anemone (not sure about if you haven't got one) you can sometimes get them to function as a family instead of a pair. This seems to get easier if you add more than 3 though, as the dominant cannot pick on the less dominant. 6 or so seems to work best but you need a large anemone, a large tank, heaps of light and a large budget as well as possibly some patience while fiddling around with the colony.