The way I see it most people know each other 1-2 y before even dating, and then date 1-2 y before introducing each other to their family, then spend 1-2 y introducing to both sides, and then finally get engaged and married within another y. So it comes out to 4-5 yrs. And that’s assuming NO breakups! So if they’re 20, or even 18, and aren’t making serious efforts towards marrying anyone they already know, there is basically no way they’re getting married by 25