What is "too closely spaced" to you? It may be different to me. It could be said that siblings born "too far apart" could also suffer consequences.

My mom had my sister and I 16 months after our brother. Consequences, sure, but there could have been consequences if we were farther apart as well.

I had my kids 3 years apart, with no birth control in between. In my opinion, the spacing of children that is all right or all wrong. What works for some may not work at all for others. Everybody is different.