We make decisions on the basis of what is best for our family. There are four of us and our needs and wants do not always synchronise, so we don't each always get what we'd really like. The children do not automatically get what is best for them because that may be a problem for dh or I (or because we only realise afterward that things didn't work out as we had hoped, or because something that really suited ds didn't suit dd, and vice versa). Like most families we compromise, and again like most families that works OK. I don't anticipate that my children will be any more screwed up than I was, and my mother was a SAHM (our early childhood was the happiest days of her life apparently, and no that doesn't make me feel anything in particular, apart from a bit sad for her that everything after was a bit of a downer, including obviously our teenage years).
Oh, and I didn't decide to have babies. dh wanted a family, and so we made the decision to start down that road. Neither of us are keen on babies, so we found someone who loved them to look after them. Result all round really, babies for the person who loves to spend time with babies, lots of hugs and love for the children, and a balance for dh and me. We'll be their parents for decades, so I don't really get the focus on the first year or two, there is plenty of stuff later that is just as important, but where finding a substitute parent is much much harder.
Luckily my mother and FIL who I know perfectly well think that mums should stay at home managed not to say anything too hurtful when the children were babies, so we got through without having to avoid them too much (which is what I expect will happen with the OP and her sister).