Remedy in case Land sold by father's cousin without consent

Our father's land property in jhunjhunu was sold by his cousin brother without our knowledge and consent on notary to many people in parts.my father's name still prevails in court books.as our family is settled in mumbai since long time ,my father rarely visited his birth place.land sold by my uncle is all occupied with residents and shops.how can we acquire this back.all this selling was done gradually by him since 20- 25 yrs back.as my father used to work in Mumbai.he didn't visited his native for a long time and we were also not informed about the selling part.