Property dispute

Hello, So, my grandfather owns a certain property in my town but he lives elsewhere with his 3 sons. Here, my dad manages that property and the property is in my father's name. Major chunk is in his name. He actually helped in buying it and maintaining it as well from past 18+ years. Now one of my uncle wants to sell the property which my father readily agrees upon (into 5 equal party i.e 4 parts for all the sons and 1 part for the grandfather himself). Last year, he(1 desperate uncle, bcz he is in debt) posted all the land details on fb with pics and valuation. And he is torturing us to death to sell the property. The property is not under his name also, and he has no write to sell on FACEBOOK on his behalf. Search for a buyer is on, but due to demonetisation nobody is coming forward to buy it, bcz its quite big. And again 2-3 days back he used all the property images with the picture of my dad on Facebook with much lower valuation and without the consent of my dad. Is it legal to do this. Is thr any legal boundaries for him. He is actually reducing the value of the land and demafing my dad's name in the whole town ( he actually has all the friends added on his Facebook account from our town also). His wife is threatening us too (she is sending whatsapp messages regularly of giving them money otherwise). They have sent many whatsapp messages to run bulldozer over our property and many threatening stuffs. The main crux is that, he doesn't own anything. And still he is posting stuffs on fb with my dad's images. And my dad is managing the property from almost 18 years. 60-70% property is under his name. And my DAD is ready to SELL it. But buyer is unavailable due to slow market. Help us with any case or something to stop him. My chacha actually threatened me on our family whatsapp group also, (and he was very well aware that only I was thr from my family). Waiting for an early reply asap. Thanks in advance Preeti