Succession rights

My paternal grandfather died in May 2021 without any will known to us. He had 4 living children 2 married daughter and 2 son.He owned one shop( on the name of my grandmother who died in 2004) and one house. Shop is in possession of my uncle (chacha) but is on the name of my grandmother in nagarpalika records, house is shared by both families. My father has 3 daughter and no son. My chacha has son. So on this ground my chacha claims that all immovable property belongs to him and he says that he has some proof which he never shows to us..now all time tries to intimidate my parents and harass them and also deny any share in shop or house. I assume that they have some forged papers or fraud wills ,as per my information their is no legal will.Please advice.