Oh my best friend hasn't been in a formal relationship and I hope he doesn't forget to hang out with me when he does.
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Marrying at 23 does seem young for men as they are generally a few years older than their spouse. But hey, we all have different expectations. To me, raising a family is more concerning than marriage (go hand-in-hand but aren't the same).
By the time a married couple is 40, they would lose a lot ambition in their education and career. They would start paying more attention to enjoying what they have already and what they can do with the current state of the family. At that point, you could either have kids in their mid/late teens or kids that are less than 10. It makes quite a difference in your life. Especially when your overgrown kids move out. You'd still have many years of just the two of you. And then you hit that mid-age where you begin to notice your mental deterioration and possibly lose the drive to do things you wanted to do.