Is it normal to crush on guys younger than me?

I don't know what it is, but I seem to develop feelings for younger guys. The age gap has been anywhere between a few months to a few years. I have/had (not sure which at the moment) a 2-year-long (and possibly counting) crush on someone who is 4 1/2 ears younger than me. The next youngest is 4 years younger. I'm almost 20. Before you all think I'm creepy (if you don't already), rest assured I'm not acting on these feelings and I may be totally wrong with how I translated them. I've liked plenty of guys who are older than me as well, but that's definitely normal. I'm just not sure how to feel about the age gap going the other way.