I have 1 son, and I wouldn't say it's that hard to take care of 2 or 3. Greater than 4 would be a problem though, considering I'm not that active enough for so many kids, so yeah.. greater than 4 would be a problem.
I have one kid in total, it's a 12 year old boy that attends elementary school in Canada in grade 8. Yeah, I would consider 2 kids a lot, because 1 kid is so hard to maintain from my experience.. of course everyone's differs, but yeah, that's only my opinion
I have 1 kid, and I never want less, nor do I ever want more. It just seems like such a perfect number for me, and maybe it's just because I never had any different number, but any more than 1 would be just too much to handle. Telling by some of the other replies, I guess everyone's got their own opinions entitled to their own experiences.