I'm on the fence about siblings. Love my sister, but don't really like her. She's got that entitled attitude - not much sympathy for the struggle of people out there (because she overcame it). I told her the other, "it's not about being right, it's about how you make people feel." Hopefully, she eases up a bit because going over to her house and her acting like a little Napoleon gets everyone's jimmies rustled. She is also 6 years older than me so we never had many shared memories after a certain point (hard to relate now). I've had the same friends since 4th grade though and they are like brothers to me - shared our struggle with learning to get girls, getting by in high school, and getting to the right point in life now.
If you are a parent and going to have kids hopefully you have them close together. That bond is a lot better (at least from what I see with my friends/their siblings).