I have five siblings. Four are younger than me, but the oldest one, my sister, is one of my best friends. We watch movies and play video games together (she kicks ass at Tekken).
We all have bonded together because we all have been though so much together, that we all rely and depend on each other. My 13 year old sister and I have bonded more since my older sister moved out, and I love the relationship that we have.
As for my 12 year old brother, we watch cartoons (Regualr Show and Adventure Time FTW!) together and play video games (I have beaten every Gears of War game with him). I share a room with him, so we have a cool brotherly bond.
My youngest siblings (7 and 9, respectively) are kind of the outcasts in the family. They are the babies of our family and they get away with everything. But other than minor annoyances, they are still fun kids.
My older sister and I have basically raised all of our siblings, so we represnt a kind of other mother and father figures.
All in all, I love my siblings. I feel bad for the people who hate their siblings. They are really missing something great in their lives.
BTW: Good thread, bro. This is a good topic.