I am the oldest of 4; we were born over a 10 year time span. I love my brother and sisters, but they each have brought their stress and drama into our relationships over the years. Nothing permanent, but at any given time I have had a sib who has stopped talking to the rest of us for months on end, or longer. (I, in retrospect, am perfect and I'm sure none of them would complain about me... they wouldn't dare!
). DH is #5 of 7 kids, youngest of the four boys, and the stories are legend! They all get along well now as adults, but were contentious as kids, to say the least. I am sure his parents' divorce when DH was 14 didn't help, but these are kids who fought with each other long and hard, and bloodshed wasn't uncommon. (Neither were threats to hang the kitten (literally) if sibling X didn't do what sibling Y wanted.) My MIL did the best she could, raising 7 kids, working full time, and dealing with a philandering husband.
Our DD is an only. I had her when I was 37, and it was a hard labor and delivery, and ended up with a 43 week pregnancy, a broken pelvis, and a post-partum infection that almost killed me. Needless to say, I wasn't interested in "trying again" right away. However, when DD was 4, I was pregnant again. I just couldn't believe it. I wasn't thrilled at all- more like in shock. I didn't want to have another child. It wasn't fear of another god-awful pregnancy or anything like that; I just knew I didn't want another child. One is a good number for me. Of course, the OB/GYN office was packed with patients, and I couldn't get a first appointment until I was 6 weeks along. However, the morning I was supposed to go for the first U/S, I miscarried. People are always shocked when I say this, but it really didn't bother me. I knew I didn't want to have another child. Don't get me wrong, I am sure I would have fallen in love with the new baby and raised him/her with endless love, but I just knew that one child was all I really wanted to have in my family.
DD20 (WOW how'd THAT happen?) is now a junior in college, dean's list student, VP of her sorority, teaches 5 dance classes a week, and dances with two ballet companies as a soloist in one and a demi-soloist in the other, so I don't think being an only has left her shy or introverted, or spoiled (can't work your way up through a ballet corps as a high schooler if you are self-centered!. Growing up she went through periods of wishing she had a sibling, but she says it was always more in passing and never really bothered her that much. She was often horrified by the mess and confusion in the homes of friends where there were 4 or 5 kids and admits that she was often happy to return to the peace and orderliness of our home. DD went on many trips with us and enjoys my company. In fact, we always offered to take friends to Disney with us, but usually DD turned us down; she was always disappointed when her friends would come with us, thinking "vacation" meant "laze by the pool all day and eat junk food." Several of those vacations weren't much fun.
Oddly enough, in the past few months I have found myself wondering about whether we should have had that second child. Maybe it's easier to consider, knowing that that ship has sailed, and I'm guessing that it's because DD is really away at school and we don't see much of her this year (college is in the town we live in). I don't know... but I don't dwell on it, and don't regret the decisions we made. It worked for all three of us!