Is it normal to not have everything in your life planned out?

I am 20. Quite a few people that I went to high school with are married and have kids already.

I feel so weird because that isn’t even in my goals. Like, I just want to finish college and get a job. Having kids is not a plan and marriage is a “if it happens, it happens” kind of thing. I am not sure how to plan for falling in love when that happens by chance.

Is it immature to not have many plans outside of getting a car, moving out, graduating and getting a job? What age am I supposed to start thinking about marriage and all that? 20 seems too young.