Wrong Name registered in Parivaar Register by Illegitimate child

We're living in hindu family in UP and my father was married around 1970-80 but he left his first wife due to her different relationship with other person but she have one child which was not born from my father as he noted since begaining. Later my father got married and now we're son of his 2nd wife and living with father in from childhood and 1st wife got mairred with some other person too. Now 1st wife's son used their power and have add his name in our family (Parivaar) Register Record without my father acceptance and also shown 2nd mother(our mother) as his mother in record. And also from childhood 1st wife's son is not living with our family too. Since he added his name in record he is trying to get share in my father's ancestral property and assets. Although my father was unable to take any action when that's all happened but now we want to remove his name from parivaar register and also want to know how we can file a case against him. Any advise can give us right direction.