I have a younger sister and to be completely honest my life wouldnt be any less different if I were the only child.
As for children....I dont want any. Dont really care who's gonna be an aunt or uncle to whom. Kids are expansive, they never go away, you have to take them everywhere with you, there is no more time for yourself. Right now I can call my boss and tell him I'm leaving work early, go home, pack my bags and just go on any vacation. Cant do that with kids. Cant stay out late with kids, cant take em with you to some places. They cry, scream, dont sit still, get annoying...the more of them there are the more they cost..etc...etc. Funny thing is I actually like kids AS LONG AS I CAN RETURN THEM.
I have friends that have kids. I see how it is and ....HELL NO! You cant invite them anywhere cause the kids have to go too and even if you could they'd leave soon after cause the kids need to go to bed.
On the other hand...dogs cost money too for the first year, then its just food and occasional vet visit. Dogs are ALWAYS happy to see you, they will NEVER not be loyal, they will ALWAYS give their lives to protect the pack (they dont know your an "owner" just an Alpha dog). Humans (in a general sence) change their minds, grow to dislike eachother, stab eachother in theback, kill each other for sport, hurt each other for fun. Lock your wife and your dog in a trunk of a car for a day. Then open it and see who still loves you!
Ive got nothing against people but dogs make better people then humans do