When i look at Jefferson and Jonathan, i see a difference. Not one like "everyone's different", but one of even though being brothers, they handle things differently. Perhaps it might be due to the age also.

Jeff is 4? About there. Jon is almost 1 i think, if not already 1.

I would think Jon is still a baby, someone who can't express himself clearly in terms of needs and wants. Whereas Jeff is verbally-abled and he's actually smart.

Imagine, if both of them are to be in an aeroplane. Think of the time when you first took an airplane. The experience, and everything relating to it. Someone who is 1 year old might feel uncomfortable with all the air pressure and stuff and maybe the air sickness. He would most probably cry to voice out his displeasure. But for someone who is 4 or 5, someone who can understand commands and knows who his parents are, what exactly is running through his mind? Fear? Feeling of which he needs to be obedient and cannot cry because his parents say so? So there he sits in his seat, pushing all those negative feelings down that tiny body of his. Except, perhaps things aren't like that for all. Maybe he is feeling joyful at having such an experience. Awed maybe, scared? Nah...