Legal question

Hi.. I'm new hear and have a question for my brother (he dosn't have a computer). My brother just recently found out that one of his ex-girlfrinds has a daughter that might be his. (he's happy about it and getting the test but they are 99% sure it is his) problem is that another guy is listed on birth certificate and he waived his parental rights to let the daughter to be adopted by the man the mother married. the mother is now divorced from the man who adopted the daughter and found out that my brother might be the father. and is now trying to get out of child support.. what my brother is wondering is if the adoption is still legal and the ex husband has to still pay child support or was the adoption nullified by that fact that biological father (my brother) didn't sign off on the adoption? thanks for any help.....