Cousin troubling my mother

My late father was the eldest of the 3 brothers.My mother is staying in a joint property which has not yet been divided among the uncles. One of my cousin is raising difficulties to stay in property like locking the most of the rooms and keeping the keys to himself, when asked to open the room he says it belongs to him, throwing away my mother’s belongings from that room, intentionally cutting the lines of the electricity in the common passage etc. not only my mother is facing issues, my other uncle’s family is also quite distressed because of him. They are all seniors citizens with serious illness , so scared to take a major step. I stay quite away to visit the place frequently. What legal steps can I take to make them feel safe?