Shannon and Kanon.

...okay fine I know that's cheating, they aren't actually siblings.

I'll have to give it to the Ushiromiya adults, Krauss, Eva, Rudolf and Rosa.



I love how in spite of how they all pretty much hate each other's guts you can still just feel that they're siblings, with a history of being brought up together and knowing each other better than anyone. And they each have their own lives and individual families as well which even if they have trouble they do love dearly (yes even Rosa :P). I've never seen an adult cast as human and fleshed out as them anywhere else.

Honorable mention to Kyousuke and Rin Natsume.



Ironically the reasons I like them are pretty much the exact opposite of why I like the Ushiromiyas. They're both such loveable characters and you really feel how much they care for each other.