Hm... I've seen FMA (both series), and there definitely was a good amount of sibling relationship building there. Can't really say I've seen Naruto--I watched about a hundred episodes in, what, ninth grade? But any interest I had in the storyline was quickly squashed by the fillers. And the horrid, horrid, horrid voice acting (this was before I discovered the joys of subtitles. I watched the English dub. *twitch of horror*). Have not seen Supernatural or much of Darker than Black... I think I watched part of an episode of DtB, but it looked waaaaay too dark for my tastes at the time. Sometimes I enjoy dark. Sometimes when I see dark shows I immediately switch 'em off and turn to something adorable and lighthearted.
I watched Madoka this weekend.
...holy crap. That's all I can say. I think I was horrified. But I couldn't really tell. I think possibly Kyubey is the most terrifying thing I have ever seen in any anime. Ever. Ever.
Watching it has definitely caused a shift in my viewing tastes, though. I'm back to being solidly in the lighthearted-comedy mindset. So I'm watching DenYuuDen again, which granted is really freaking depressing near the end, but it makes me happy because it's so awesome. I think I might re-watch Blue Exorcist soon, too. I'm in a nostalgic phase, apparently. (I want to read the DenYuuDen light novels. And a second season. I want more of the story, dangit! TT.TT)
Maybe when I get into more of a dark show mood, I'll try Darker than Black again... hrm.