A few weeks ago, I was putting Miss E down for her nap. We were in her bed, Baby Z between us. Miss E looked at me and asked, "Does the baby cry because he misses B?" (B=Baby Z's birth mother).
I was floored that my four-year-old would think to ask such a question.
I replied, "Probably sometimes. Do you miss your birth mother sometimes?"
Miss E, "Yeah."
Conversations like this make many adoptive parents very uncomfortable. I talk a lot about this subject in my book: open adoption, the Primal Wound, etc.
If you haven't yet read Nancy Verrier's book The Primal Wound: Understanding the Adopted Child, I encourage you to do so. It is a one-of-a-kind book.
Granted, I was very resistant to the Primal Wound concept (which occurs when the bonding process between mother and child ceases to continue after the baby is born, resulting in "abandonment and loss" which is "indelibly imprinted upon the unconscious minds of these children"---Verrier pg. 1) when I was waiting to adopt my first child and even after her arrival. Why? Because it's messy and painful and complicated.
There are stacks of books for adoptive parents and prospective adoptive parents. But there are very few which explain and support adoptees and birth parents. I hope in the future, we will see more and more publications from the perspectives of adoptees and birth parents, but until then, start by reading Verrier's book. You will gain insight that will no doubt benefit your parenting!
But so is adoption.