I am a senior and i like a freshman 10 points?

I like this boy he and me have known each other since his sister played softball with mine and he is also a twin like me. The think is he is a freshman and i am a senior and i don't know since i am about to graduate if i should get involved with him. Just today Kris came in and was taking his test and lipped mouthed to me I love you and i said it back to him and i told him i liked him and he said that he would think about dating me. The thing is he is really sweet and the only one out of him and kyle that is not mean to me. So my question is should i get involved with a freshman about to be Sopre after i graduate. But the thing is he says he wont see me after graduation and i told him that we would. Also there is an age difference i am 18 about to be 19 and he is 15! So what happens if we start dating? He supposedly likes me a lot. Is that fine? Do you guys find that weird?