How can I "act" like someone's aunt?

This is the scenario: An adopted child (tom) feels very comfortable with his adopted mom and dad, However, he does not get along with the rest of his adopted family (his aunt and uncle) and the reason for this is because he feels that he does not "belong" or "fit in" with them. He feels distant when with them, and this distance comes across as rude to the Aunt and Uncle. Tom always make short, snide remarks that seem rude to his aunt and uncle, but he's really just feeling uncomfortable around them. Anyway, I am the aunt, and our group is presenting this on stage in front of the rest of the cl ( I'm in high school) and I'm not sure how the aunt should greet Tom when he walks in through the door...I mean I couldn't pull of the "hey honey, give uncle judy a hug" could I? lol I mean it would be kinda hard because as his aunt, I obviously love him and want the best for him, but at the same time I think he is very rude so don't if I should come off as friendly? His uncle is friendly lol Oh and the reason he is walking through the door to our house is because we having a huge family dinner and he is invited and he is late.