My brothers and I have a 5 year gap between the three of us - We're all fairly close and it seemed to work pretty well with my mum. Mum got pregnant the year I was in Prep, so I was at school and she didn't have to worry about me when my brother was a baby. Then the same happened when said brother was in kinder.

I'm much closer to my middle brother than the younger one, but that could just be personality clash (we're fairly similar in our stubborness and short temper but not really much else)