Implications of breaking engagement

Hi, my cousin got engaged couple of months ago. The marriage was fixed for August. The girl now confess that she has some health issues with regard to spinal cord. It seems she cannot work for long hours, cannot lift weight and cannot gain weight. Thinking about future and also feeling like the girl's parents cheated before informing about her health condition before engagement, my cousin's family decided to break the engagement. They want to break it amicably, ready to reimburse but the girl's family is threatening about going to police and getting my cousing arrested. He doesn't have father and my father is the only male support to them to do any talks. My father is also old and diabetic, BP, and have other health issues. His mother (my aunt) is also diabetic and recently undergone orthopedic surgery. We do not want any quarrel or fights but they started shouting at my aunt and father when they visited the girl's family. They are ready for all type of fights, but we want to end things smoothly. They deny her health issues, they say we can take the girl to doctor if we want. Initially they said they will give the health report but later changed their stand. What can we do now?