My sister and I are about as different as 2 people could get, if we had not been sisters we would likely have just avoided our respective types forever. She is the quiet study hard, pay your dues, don't rock the boat type and I, the live life by the seat of your pants type. I think that the reason we are so close is because of how close in age we are (1yr and 8months to be exact). Even today we talk often and though our lives are vastly different, we can always lend an ear and offer some advice.
There was a time when I was completely convinced that kids should be 3 years apart, to the point where AR is 3 years older than EE and she is 3 years older than HG. Then came SL, 1 year and 7 months later and IL 25 months later. My little ones are so much closer than my older children. EE's down syndrome has kept her around the same developmental age as HG and it helps that they are about the same height. They are very close (the fight enough to prove it, lol), I hope that never changes. IL and SL are inseparable, they make each other laugh and no one else gets what they are laughing at. I love that. AR keeps asking that we adopt a big brother so that he will have someone older to talk to, but truth be told he and HG have a really special relationship that is like none of the others. She believes everything he says and he teaches her everything he knows. They are 6 years apart though, so we'll see how long he enjoys having his own personal tag-a-long, lol :)
Well, I hope you all get to enjoy your siblings and raise your kids to be each others best friends. :)