Question about an allegedly Father in a Foster to Adopt situation

Hi, My wife and I are fostering to adopt a baby boy since he was 6 days old, and he is over 7 months now. The biological mother has not done anything to get him back, but now that the 6 month court date is approaching she started to visit. DCFS will recommend that her reunification services be terminated in the next hearing. In the beginning of the case she told the department and court that guy "X" was the father, and the baby even has his last name. Guy "X" didn't come forward and his reunification rights were terminated. Now that BM knows that she is not getting the Kid back her and her mother are saying that there is another guy (guy "Y") and he is the real father. They are being very aggressive and even tried to bring Guy Y to a visit.Can Guy Y just show up in court and say that he is the Father? Is the Court going to request DNA testing ? The reunification rights were already terminated for father X. Can she bring another guy now and say he is the father? Does anyone being in a situation like that before? BM has not mentioned Guy Y at all until now, and told the court that guy X was the father? Biological family Think that Guy Y will get the baby back next court date. We know is not true. We are very concerned about this guy claiming to be the father. Any information would be appreciated