Adopting a child who could be addicted.

Ok so my brother has made some very bad choices in his life. Including women drugs and bad social behavior. He recently found out that he's going to be a father again (#5). He knows that my husband and I have fertility problems. He has asked us to adopt the baby. My heart say YES!!! But i know the child could be disabled. She hasn't had any prenatal care. Should we do it? There both gonna sign there rights over.