I am trying to find this story - I only remember the setting: a species which has four genders. Any three of them can come together and "wurple", which would produces a member of the missing gender. The main character seems to think this would automatically keep the population distribution in check, but it's not explained very clearly.
The story is the thoughts and anticipations of one of them as he plans different "wurples" he would participate in. He was especially fascinated with just the word "wurple". Each of the four genders has different characteristics, and one is currently much more prevalent than the others, so much so that nobody wants to associate with them - but that just makes the problem worse. Any ideas? I would probably have read it in the early 90s or before.