It depends on where you live I guess, here in Texas its too hot to wear 2 layers. You'll just have to make the judgment on if you think your baby should wear more than one layer.

I dont do it during the summer time

My family has always done it. It's normal to me.

I've seen it done pretty often unless it's super hot.

With both my boys I always put onesies under most their clothes. mainly just my 10 month old now though, with my 1 year old (2 in 2 days lol) I just put them under his sleepers. Everyone I know does it too. lol.

I've never heard of putting a onesie under a different set of clothes unless the clothes don't have sleeves and u want sleeves on them

That me though. Also I'm pregnant with my first, and seeing your post is my first time hearing it.

Honestly I never herd of this with any three kids. I just put PJs, and I use onesie as a shirt because that's what it is.

I do . I just feel like kids need two layers always