I'm 22. Wanting children would make an insane person.
This is the correct answer. Maybe it'll happen at some point, but it's certainly not something I have any interest in now.
There are pros and cons for having kids young, probably more cons overall, but the pro of being young enough to enjoy life after they leave is a huge one. It seems like it would suck to be in your 60s when your last kid leaves the house. It's probably best to wait though.
I was 24 when I had my daughter. It was a totally an unexpected and life changing experience. Maybe it would be nice to "have my old life back", but my life has purpose now. The main purpose in life is to reproduce, everything else in life is finding ways to sustain your life so that you can reproduce. So, I feel like I've done my duty to the human race.
Another thing about having children young is that biologically, we're supposed to have children at a young age. You also have enough energy to look after it properly.