My son called friend is pregnant and saying she is 17 weeks. But she kept telling us and family members that baby daddy…

My son called friend is pregnant and saying she is 17 weeks. But she kept telling us and family members that baby daddy is my cousin in law. She have one period in a year. Her last period was in April 26. But she didn't met my cousin in law until May 3 the day they have sex. She have another kids from three different men. Now it doesn't make no sense cause she can't be 17 weeks if it is my cousin in law baby. They both have sex at my house. She should be 14 weeks now not 17 weeks. So we have a feeling there is someone else she have sex with but doesn't wanna said. So all we ask her is for DNA test to prove it it is my cousin in law baby or not.