ETA: just saw it’s a resurrected zombie post. Hope you found someone OP.
They don’t need to be childless. I’ve adopted an extra adult. He lives with us, is very much part of our family and is like an extra son to me. We are often mistaken for mother & son.
My mum became very close to a neighbour who had limited family & they very much had a mother/daughter relationship. In fact I used to call her Granny.
I’m not sure any of this can be forced though. In both cases a close friendship came first. In both cases there was something about that inter generational friendship that developed. I think in my mum’s case she filled the caring daughter role as that was the gap - and my mum became POA/next of kin/looked after her when she became elderly/nursed her at home in her final illness. But she was treated a family for years before. She’s in every Christmas dinner photo throughout my later childhood, teen years and into adulthood. Sat next to my aunts & grandparents. I used to go and have a cup of tea with her after school throughout sixth form.
In my case the gap is the mum gap and that’s what has developed. It is recognised by us, my family, his friends and more formally when he had medical treatment (I was the next of kin/point of contact).
it is very rewarding for everyone to collect extra family members :lol:- especially when life can make it really hard to make new friendships - but I’m not sure what it would be like to have to look for them if that makes sense. In both cases we weren’t looking for anyone - it was just something that developed naturally from a close friendship & connection & it’s that that makes it authentic.
Good luck though - I hope you find someone.