Let me know if you guys are okay with the dynamic of Sam being a sort of protective in a way of running interference for his sister to make sure she enjoys herself as much as she could. I sort of see it as overcoming his normal shyness when he's doing it so she doesn't have to put up with it. It could be something that she's noticed and thinks is cute (because of the situations it leads Sam to being it), or that she hasn't realized he does it because she's having too much fun to notice, or that it's just sort of thing she expects of him without realizing it (I don't see her actively demanding it)? Whatever you feel suits them best Anna. :)