I believe God would approve of any relationship that was founded on mutual love and respect.

In a marriage you seek to become a lifelong partner with someone else. You are choosing to live the rest of your lives as a team and to create a new family unit for yourselves. A relationship between a man and a boy does not resemble that in any way. Therefore, I think that applying marriage terms to an AF/YF relationship wouldn't make a whole lot of sense.

I don't disagree with traditional marriage ideals. But they are just that, ideals for marriage. I don't think it is correct to apply those ideals to other kinds of relationships which have nothing to do with marriage.