Hi CatOutOfHell sorry you and our partner are struggling with this. There is a book called
Adopting After Infertility
I am not sure it is brilliant but it is a start.
To address a few of your concerns and concious that I may wildy offend readers here but.....
You do not parent someone else's child. They legally become your child, but of course they do (except in exceptional circumstances when birth parents have died) have other parents out there. In some circumstances you can maintain contact with them through letter box once a year.
For me the route to adoption went via donor eggs, so I got used to the idea first that my child would not be genetically linked to me, but they would biologically have come through my body, not the case for dad's of course. once I got used to this idea it was very easy to see that it did not mater what combination of DNA had made up my child.
I am a birth mum to a dd and an aunty to two boys. I love my nephews and although there is a genetic link with my sister and me and my sister and her kids if I had discovered that actually my nephews (or my own birth child) had been 'swapped at birth' I would love them just as much.
I love my friends' kids. I care about them and I sometimes look after them and give them as much care as my own. It is a massive leap from having a friend's kid stay over to adopting but for me it made me realise that all kids need love.
Lastly, I come from a long line of animal lovers. My gran, my dad and I are all cat crazy and before that we had a hamster we adored! They were not even the same species as us but we loved them and cared for them. I am not saying having a cat or a hamster is like adopting. Honestly 100% I am not. I am just saying that parenting is all part of loving and once you begin to love you find it grows.
But he is right to explore all this and work it through himself.
Apologies to anyone I have offended, but I wanted to be honest with the OP that all I have said here is true for me.
I have also heard of kids who cared more for pets than grandparents etc. I really did think about all the loving relationships in my life and I knew that DND played very little role in them.
All the best.