Bigger, I was the middle of 3 and I have 4, I do have a similar family dynamic though, my sister and I are close in age (18months apart) and my brother is 15 years younger. My children are 17 months apart then a 13 year gap before having 2 more at 20 months apart.
It worked well for me as a child/teenager and it seems to be working well with my family too