Vickie,
I believe you are a very intellegent and loving woman. I think you answered your question in your post. I don't believe, as much as you want to help this little one, that it is best for the family you have now. There are a lot of dynamics that could blow at any molment.
At this point, I would pray that the Aunt comes through and he has some family connection to grow with. Take it a day at a time.
You are a good woman. The best will happen for all.
Sharon