Help please

My dad is basically married twice . Back story: my dad is a ASI one star police officer He already had a wife and a daughter and after a few years he married my mom without telling my mom about his first marriage (and my mom has a marriage certificate too ) . After a few years he told my mother about all these things but my mother preferred to be quite as it could have hampered his first family as well as us. This matter was hidden from the first family for over 21 years. A few days earlier his first family got to know about us and ever since they have been troubling us and my dad . And his daughter( who is 26) posted vulgar comments on my Facebook post she also called all of my dad's friend, police colleagues, his seniors and so on and told everyone about this matter. His first family has been constantly harassing him . He owns 4 flats in Mumbai which are on his name Within 4 months he is going to get retired so what do we do ? And his first daughter has been trying to do all the things to put him down . Also she wrote an email complaint to the ACP and told him about this matter The person writing this is his second daughter from his second marriage.(I'm 20 years old) What do we do about this? I'm very scared that he might lose his job and he can be behind the bars and all of that stuff please help me out.