This doesn’t happen in nuclear families only when it’s a child of divorce. I was 5 when my sister was born and I was very jealous. I wasn’t coddled at all in fact I had to learn that she was my sister period but for some reason in these types of families it’s almost a crime to have more children. I can remember a time when I was pregnant with my second and we were out to dinner with my in-laws. They not only didn’t care about how I was feeling but didn’t acknowledge my son either. Kept saying OMG SD you’re going to be a big sister again. Fawning all over her but no one addressed my son and acknowledging that he was going to be a big brother. I had to have surgery to carry both my babies to term and that wasn’t acknowledged either. No “how are you feeling since the surgery” I have to say it’s really hard for me to look at my in-laws with any kind of warmth because it was all about SD and all about the guilt. I really don’t understand why these people bother getting divorced if this is what that are going to do.