Wow!!! This is very uncommon and under normal circumstances I would say that age should not be a factor but you will really need to consider the issues that certainly would be evident later as you progress through life.
Being a very young woman, you are still maturing somewhat, still trying to feel your way through life, while he most certainly is at the point where he is settling in.
Before you jump head first into this arrangement, I would look at all of the pros and cons associated with this love fest and decide what is best for the future for both of you because that is what a family is truly based on.
I hope this helps!