Reversal?

I adopted my husband's child from a previous marriage about 2 years ago. His bio mother tragically died 2 weeks after giving birth to him. After a year and a half court battle with my husband's parents, who tried to obtain guardianship of the child, our attorney and our son's attorney advised me to adopt him. My husband agreed and asked if I would. Now he is threatening to have the adoption reversed. He constantly tells me that I am not his mother and he said that he will go to the judge and tell him that he was in distress. Is this possible? How can this be done? Advise appreciated. Daisy