Hi Sandra,
I'm sorry it's not quite clear to me if you're looking for a child that was given up for adoption or if you think an adoptee had a Glenn father and you're looking to prove that face.
Either way, my recommended first step would be to have the relative take a DNA test and upload the RAW DNA file to as many sites as possible.
There are several possibilities for the next steps depending on your answer to my original question.
You might also consult Adoption Angels by adding that tag to your original question.
Good Luck!
Shanna