17 & 20 y/o dating ?

I’m 17 and this guy I really like is 20. I do consider myself mature and most of my friends are older, in their 20s. I tend to flock with older people, however from his standpoint do you think 17 is too young. He has a little sister who is 17 so I feel that might make it seem weirder, like he’s dating one of her friends kind of thing. We get along very well though. In three years this won’t matter, but I don’t want to wait three years.