False allegation case

Hello, I would like to know about some law solutions against false allegations and their counter solution against it. My uncle's son has made a court case of 144(2) crpc against my father. According to the case he has registered that my father has tried to destroy some part of the co-shared building illegally and tried to grab it forcefully, though nothing has been done to the building nor even we knew that he has filed a case against my father. The first summon was collected by uncle's son from the police illegally with exchange of money and we did not knew about it that the first summon has already been issued. We came to know about the case when police came to deliver us the second summon. We did not even knew that the proceeding has already begun. My father is 78 years old and already underwent bypass surgery and is bedridden. What should we do now? Can we proceed a case of defamation against him of illegally harming my father's reputation both physically and mentally? My next query is that- The building about which the case he has registered was of our grand father's. He gifted it to his four sons which includes my father as well. Out of four son of my grand father, only my father survives now and rest of my uncle has died. Does my uncle's son automatically becomes the co-sharer of the building? Though none of us stay in that building as my uncle's son resides with their family. The building is more than 65 years old. None of my grand father's son has said or written anywhere that the property will be inherited to their children after their death.What should we do? Please advice something. Thank you.