Usually in fiction when people write sibling they (imo) either write them mean towards one another or extremely kind towards each other but I have yet to see my sibling hood dynamic and I think it would go PERFECTLY with the lan brother.
My sister and I have ‘conventions’ basically set of rules we agree upon. Can be weirdly specific thing like ‘eating one sandwich is strange, why would anyone do that ? Sandwich should be eaten in TWO or not at all. ’ And ‘zucchini are disgusting demonic thing ’(THEY DO NOT TASTE LIKE WATER GET YOURSELVES A NEW TONGUE IF YOU THINK THEY DO) or rule that we put in place because the alternative tired us by just imagining it for exemple this one we agree upon when we were children : ‘if one of us put soap on the other toothbrush and the other retaliates it will just never end. So let’s not even begin to do that.’ This rule act against any prank actually lol
Anyway, I think it would be extremely funny if teen wwx BAFLED by this sibling dynamic lol (wwx : why do you mean you have even MORE rules ???)