I'm in a relationship with a guy younger than me, It's fine. I don't completely agree with people dating when they're younger, But in terms of moral matters and stuff, It isn't wrong per say. I think there's a Romeo and Julliet law or something that says if you've been dating when you're underage and one of you hits 18 before the other, Within a certain age range you can still legally date them or something.
Just make sure that the person you're dating is able to give consent to dating and they are mature or otherwise it won't work.
So you are 15 and he’s 13 I don’t think it’s wrong because you can love who you want and age is just a number and if he likes you back than there is nothing wrong to date him at least that’s what I think and you’re young so I would say just try it and if it doesn’t work let him go