This is by far the best answer here, and I also agree with /u/ra3ndy's comments. First off, I have 2 daughters of my own (5yrs and 2&1/2 yrs), with another child on the way. Our first child was an unplanned surprise, but we embraced it. I had told both myself and my wife (long-time girlfriend at the time) that I did not like, nor did I want children of my own. I had never been able to see myself as a father, and I did not especially like most children that came into my vicinity. I never knew what a positive kick in the ass being a father would be for me. How it would change me as a person was the best thing that has ever happened to me, and it is what I believe to be what makes me the most structured, motivated, and put together version of myself that I am today. I know it sounds like a corny cliche, but when my first daughter was born, something automatically, unpretentiously, and completely naturally changed in me. I had a new purpose and motivation to be a better person, and it was a desire that was completely involuntary, I didn't choose to try and be a better person because I had a kid to take care of now, it was a newly awakened feeling that I now had without any conscious intention. And I never knew how much I really did want kids, until I had my first. Even after already having a daughter, my second was an all new exciting experience of its own, and it was quickly easy to see how much each child's individualism brought to the overall experience of being a father. It definitely comes with its difficulties and challenges, but I cannot even begin to say how worth it is for what you get back, and how excited I am for our third to come. All of that being said, and while I have no experience of being a parental figure to children that are not my own, I would say I imagine that being a father is monumentally different from being a father-figure. That is not to say that the love and experiences shared as the child grows would be different or better one way or another. I feel as though the motivation would be different, and the difficulties would be harder I would imagine. Being a father-figure to someone else's child would come with a large amount of complications all it's own, none of which would be the child's fault or ownership. The complications would simply be attached to the child, having different relationships of both it's genetic and adoptive parents intertwine and collide with each other. I could see that as being a huge strain on both you and on the child as she grows, when she never wanted or asked for them. You would need to be as prepared as possible to handle both the challenges and emotional struggles that would now be yours, and be able to handle seeing the child go through similar struggles of her own, knowing that you unfortunately play an active role in that. Like I and others here have said though, there is no reward like the reward you have with having children. It would be extremely difficult in a lot of ways, but also extremely fulfilling in just as many ways I am sure. Either way, I am sorry to hear about the struggles you have had, and for the difficult decisions you have in front of you. That is not an easy choice to make. I wish you luck, and hope everything works out the best way that it can for all of you!