Why did everyone get married and have kids so young?

Admittedly this is a not a critique of the Naruto ending so much as a minor nitpick: why did all the characters who got married and have kids did it so young and all at the same time?? I’m shocked at how fast and how young Naruto and Hinata, and the other characters got married and had kids so young and so fast at the same time. Like Naruto and Hinata dated for a year, got engaged they both got married at 19 and had boruto at 20 and Hima at 22. Like why it happen all so fast? To put it into perspective Naruto was 17 when the war ended, so he only got married and started a family only 2-3 years after that. It would be fine if it was just them but nearly everyone else got married and had kids at the same time. It was probably for them to all have kids in the same age range for boruto but c’mon. And literally only Naruto and Hinata had more than one kid? I find that hard to believe. Even the side characters in the original had siblings. I can get people getting married and having kids young because they can die in battle but like, that’s not the reason because it was a peaceful period. I don’t even think it’s a cultural thing in the leaf/or the ninja world at large either. I just find it really weird.