Brid, I thought I had a big family, I'm the youngest of 7 but 13 - wow! I suppose we should be cracking open the anti-depressants.
I would say we are all reasonably happy. We all have our own little problems but then who doesn't. I was just thinking yesterday about what a good job our parents had done with us as we have all turned out to be decent, hard working, caring people. I don't really see how the size of your family could effect your overall happiness though. In fact, if anything I would suggest it is the contrary. Having a big family, there is always someone I can turn to with a problem and that certainly helps.