False case for not looking after grandmom

Its about the older parents look after issue. My mother is having 3 siblings. Two are elder to her and one is younger. At present my maternal grandmother is alive. She was living with eldest son after her husband's death for 10-12 years approx. Later she shifted to her second elder son's home and then, finally to my mother's home for last 1-2 years. The youngest son has not ever visited or talked to my maternal grandmother for last 8-9years or more. We have been taking care of her but lot of time she would insist us to let her go to eldest son's home as she seems to like to stay at his home. Some of the days would be very difficult for us specially for my mom when grandmother would start yelling and shouting unncessarily citing health problems with the intention to see her eldest son or the desire to go to his home for permanent stay. She would plead my mom to call her eldest son on telephone or ask him to come and visit her. Whenever, my mom had telephoned her eldest brother he would either talk very rudely or would say 'why you don't want to look after your mother'. Lot many times my mother clarified and said that its gradmom who is insisting for a call and she is just calling so that she can maintain peace at home. Grandmom has lot many times mentioned that she is comfortable in staying with her eldest son and doesn't want to stay anywhere else but she blindly trusts her eldest son for any medical issues/ medicines and can do anything for him (we understood it when we realised that she will always speak good about him and ill about others... may be with the intention that he eldest son would some day take her with him to his home). Of late, it seems that the eldest son had some other plans in mind. He was not willing to look after grandmom and somehow wanted to avoid visiting grandmom. Please note that he has been signing the form for getting grandmom's pension every month for last 10-12 years or more. Many times we came to know that they cannot keep grandmom at their home as they want peace at their home. If grandmom lives with them then their wives are creating issues. Few days back he came to home when only grandmom and my mom were there and abused her and hit her with a chair. Suddenly, he realised that he made a mistake and he took grandmom along with her and threatened my mom that he would file a case against us for not looking after mother and would get the property (given by grandfather) back. Also, he said that he would trap my mom and father in this case. Later on he sent second elder brother of my mom to take all luggages of my grandmom from our home. Initially, we thought of filing a case against eldest brother of my mom citing that he came to home and abused and hit my mom with chair but later on we thought that it would bring shame to entire family and we decided to go to police station or court. We were informed by the second elder brother of my mother that the accused (eldest brother) has got nice reach to DIG and any action from our side would create issues for us (seems like indirect threat). Also, after waiting for 4-5 days, we got info from the second elder brother of my mom that the accused is preparing some documents to file a case against us by saying we did not look after her and the inherited property would be taken back. My grandfather has specifically written his will and gave his share (only his share not grandmom's) to my mother. Grandmom's share were distributed and given to all 3 sons. Also, it seems like in the document for grandmom's share it has been clearly mentioned that my mom doesn't have any right on grandmom's property. Of late, we came to know that the accused was not happy with the share distribution which was done like approx 35 years back. Now, my question is can a case as mentioned above by the accused against us would lead to giving back property/share to others? Please advise how to handle this case as the second elder brother of my mom has informed that the grandmom would do anything for the eldest son and the elder son seems to prepare some fake doc related to case? My grandfather's property/share was given to my mom by grandfather (without any condition and clearly mentioning that my mother is soul owner). Does this kind of false case by eldest son could impact us in anyway?