Would it be wrong or weird for a ninth grader to go out with a seventh grader?

I really like him but my sister said it would be weird if I went out wih him. And I don't know how to tell my mom that I really like him. He really likes me back bu I don't know what my fronds will say either :( so I wanted to get other peoples opinions! It would hurt my feelings just help me out! Oh and I'm 14 and he is 13