Abusing to parents for property

My father is 61 years old and he is retired hawaldar from district court and mother is 51 years old. My neighbour who are my relatives,they are abusing my father all the time and he is getting mental distrub. Our matter is we bought 1 plot of half side from my relatives (who has partition with other side half plot )and rest part of that plot is partition of 5 child including my father. We asked all 4 to give their partition by talking money. 1 is ready and rest 3 was not ready so my father started construction on that plot by taking his partition and who ready to give his partition in the construction. We have left their 3 partition like that and we took our partition and other person partition in our construction. We have bought half plot from my relatives who is blaming us now that we did registery of half plot illegally from him actually with his presence and with his acceptance Only he has given half plot to us. We have all legal documents but still on that point he and his wife and mother abusing my father actually my father is not replying to them because he is not wrong but as they are my parents so i want take legal action against that family who are abusing my father Due to this reason they are daily abusing my father with bad word and they are doing mentally harassment with my father. Please suggest what do with this neighbour because I stay away from my parents for my job purpose.