Has anyone adopted their child's baby?

My grandma and grandpa adopted my cousin when he was a baby. My aunt couldn't raise him because she had a very serious mental illness, but she was still very much a part of his life and often lived in the same house with him. Though my grandparents legally adopted him and raised him as their child, my cousin grew up calling his biological mother "Mom" and my grandma "Grandma." He called my Grandpa "Dad," though, since he didn't know his biological father. Kind of a confusing situation, but it all worked out in the end. He grew into a wonderful, compassionate man. One of my favorite cousins, for sure. (You'll notice that even though he's legally my uncle, I totally think of him as my cousin . . . )

I actually just met someone this weekend whose sister got pregnant as a teenager and her parents adopted the child. He's a few years old and knows who his birth mom is, but is being raised as if they are brother and sister. I asked if that was a difficult dynamic and they said it was really rough, especially the first year for both the birth mom and the mom. I can't even imagine how difficult it would be, but they said it has gotten a lot easier over the years. The birth mom is now in college and has said it is still hard because she feels motherly instincts kick in when she is around her birth son, but she knows he is being provided for in a way that she wasn't able to do at that point in her life. I do wonder how the son will cope with this as he gets older and understands.