I think we were wired for adoption because we were made in the image of God. Ephesians 1 says this about God, "Long before he laid down earth's foundations, he had us in mind, had settled on us as the focus of his love, to be made whole and holy by his love. Long, long ago he decided to adopt us into his family through Jesus Christ." I'm not saying that everyone should adopt, but I do believe it is a natural expression of the love of God and something Adam and I were created to do.
There is a beautiful children's book by Marianne Richmond called "I Wished for You," and this excerpt so beautifully states exactly how Adam and I feel.
"All families are different. What makes a family is their LOVE for each other...I wished for you, and you are always and forever my wish come true."
I would like to add that NOTHING can change that.