Rob
Go for it mate, I think the nail was hit on the head when it was mentioned that a tad of envy could have crept in, personally I could not live like this, I have spent all my life with parents who found it very very hard to praise (no fault of theirs either, it's the way they were brought up), I would actually have to "have it out" with him, i.e. try and have a serious adult conversation as to why he is like he is with you, if you were his "real son" I wonder if he'd be the same, but hey this isn't an agony aunt column so I won't go on
Keep us informed how you go
Dean