Whenever Claire is even a little mean to Clinton, there are inevitably people who accuse her of going overboard. My opinion of these people, of course, is that they are probably only children. lol
Granted yes I know that not every pair/set of siblings is like this, but usually when you've been stuck living with someone relatively close to your age for most of your life, and they in turn have been stuck living with you for all of theirs, it doesn't matter how much you care about each other, you *are* going to get on each other's nerves, sometimes a whole heck of a lot. And yes, the catty banter is part of that wonderful package deal.
No, I just treat my younger brother like a person, you know? Yes, younger siblings are annoying, but Clinton's 21 and Claire's 24, and they're not living together any more. Clinton's living on the campus while Claire still lives at home. At this stage, sibling relationships change - you don't see each other that much any more, both are out of puberty, parents don't have that much influence any more, so you can actually enjoy the time you spend together because you don't have to spend it together at all. So, if they were 10 and 13, those insults would be normal and very usual for a sibling relationship, but they are adults now, with responsibilities and limited time. Why would you choose to spend that time with somebody who just insults you?
Your post would have some merit, IF Claire seemed like she was actually being serious. However, she doesn't, so I feel like you're being overly critical just for the sake of it (as people in these forums seem to have a habit of being). And even if I'm wrong, and she does mean some of what she says, so what if they still bug each other? It's not like they only see each other once a year and spend the rest of the time hundreds of kilometers apart. They might be living under separate roofs, but they're still in the same city, and given Clinton's age he probably hasn't been away from home for very long yet either. Their sibling dynamic probably hasn't really had the time or space to evolve beyond the "Mooooom, he won't get out of my room!" stage. A little bit of snarkiness also doesn't necessarily mean that they wouldn't still do anything to help the other out of a bind either. That's the wonderful thing about sibling relationships, you can be meaner than rattlesnakes to one another, but when the chips are down, you still have each others' backs. lol
Now granted, maybe I'm a little biased, and their relationship seems less hostile to me because their age difference and dynamic is so similar to my brother's and mine. I'm 25 (and trans too), and he's 21. We can't seem to spend more than about 5 minutes together without taking jabs at one another, but that doesn't mean we care about each other any less than we would if we were best buds. Heck, I held off transitioning for 4 years so he could go through high school without having to deal with crap from his ignorant peers because of it, and he's been supportive of me (albeit with the occasional shot taken) the entire time. Soooo you know, maybe I'm wrong and Claire really is just a mean spirited person who doesn't care about Clinton at all, and she really does view him as nothing more than a blight on her life, but I highly suspect that my whole "you're being overly critical" thing is probably closer to the mark here.
Some sibling relationships are all unicorn farts and puppy kisses, while others come just short of strangling each other with the telephone cord. What I see when I look at Clinton and Claire is a happy medium, prooobably leaning a bit more towards unicorn farts.