@ernesjohnson I wanted a sibling for a long time, by the time I got it in 12 y.o, it was kinda... meh. Plus, I was parentified, since my parents divorced shortly after. They probably would've anyway, but it made my and my sibling's experiences in life even more different, because I basically grew in a somewhat full family to some extent, and I have a relationship with our dad, which they don't, I believe it really affected them.
We're practically of different generations, plus, being an immigrant family, I still was born in the other country, and those first 4 years I spent there were also quite influential. So we're just too different, and almost no contact now, after I've been such a bad parent to them (obviously, because I wasn't sensible enough to be a parent at 18-22, I was trying to build my own life!)
Right now I see that my problems wasn't due to lack of siblings, and I'm coming in terms with my life. My LO is not so little, she's almost 10, was recently diagnosed with ASD, but I'm confident she'll be alright, we have a very strong connection, and I believe that the connections you form with your parents can be replicated to others as you grow, so with our help and guidance, and having the attention and love we give in helping her navigate the world and supporting her - she'll be fine. And if I'll finally be able to focus on myself, I hope both me and my husband will live a long life beside her, leaving her in a good place in life so she'd go on ok.
I'm sure that almost all the only children who longed for a sibling didn't have enough attention from their parents, despite being their only, that's all. When you're loved and cherished, and your needs are addressed, you don't need a home-bound- playmate or someone to commisserate with.