She is going to grow up to look exactly like Bella, and he is not going to grow older than twenty-looking sixteen. Also, he is not going to be romantically attracted to her till she is thirteen or so, when it won't be an issue, since he will always be sixteen.
I do not care for Twilight but this nonsense about Jacob being sexually attracted to a baby has GOT TO STOP. People don't even know what pedophilia is anymore so they apply it to everything. "Oh, that guy is putting gum in his pocket where the clerk won't see, reaching behind that child to do so; he must be a pedophile!"