It was pretty surprising how easy this list came to be, I guess I like a lot of TV and Book siblings! :D I thought I would have a harder time finding ones from books but in the end all of them were book siblings expect two.
1. Klaus, Violet, and Sunny Baudelaire from A Series of Unfortunate Events
2. River Tam and Simon Tam from Firefly.
5. Sookie and Ryan Stackhouse from True Blood/The Sookie Stackhouse Series