My DS decided he wanted a GF in the middle of his junior year (which was the COVID crapola year), and there was conveniently a girl interested. He went out with her as a trial GF, even told me well she isn't the one I'm really interested in but she's interested in me so I will start here. Well fast forward almost two years and they are still together
My DD had her first BF when she was 16. Again similar to my DS, she set about trying to find a BF and this boy was interested and nice and there you go, next thing you know they are dating. Lasted about one year.
Neither kid was interested in dating before this age, so 16-17. There may have been crushes prior but no actual hanging out or anything.