Yes, SO much has been written about this subject, so it should be easy. Check out Google Scholar or FindArticles.com... Start with good, peer reviewed journal articles, or that your paper will be based on quotes from good sources... like cooking with good ingredients.
Some people say that same-sex couples cannot raise a child correctly, and other people say that they certainly can. Here is one to get you started:
stanford.edu/~mrosenfe/Same-sex%20couples%20and%20their%20ch ildren,%20abstract.pdf
I have not read this, so I don't know if I agree with it or if it is any good. Look at this ignorant one, not peer-reviewed: ewtn.com/library/ISSUES/ZSSADOPT.HTM
Kevin, EssayForum.com