Oldest to youngest my kids are 3.5 years apart. Two girls then a boy. I don't think its the 3rd that puts me over the edge but rather my son's personality and needs that are much much different than my girls. I love having 3, couldn't imagine not, would even consider a 4th if I was a little younger. But my son is 4.5 now and still cries for me to lay with him everynight and I just think my oldest was 3.5 with 2 younger than her, what would we have done if she was as difficult as he is at times. Even the 2 year old. I will say though the transition to 3 was cake. It was a divide and conquer strategy for us, one would take the girls the other the baby.