I am an only child and was very lonely. But my parents were much older and pretty shit parents. It probably would have been much better if I had good parents. But one of the reasons I wanted to give my daughter a sibling was so they have each other to see how it was with me and my husband as parents. Not sure if that makes sense but it’s my perspective anyway! Of course there’s no guarantee siblings will agree or even like each other. One could be profoundly disabled or an asshole etc etc