how can partition of ancestral house be initiated

My grandfather had four sons and had four independently houses built on separate piece of land. Location is Village Haat, Dwarahat, Almora. these four houses were allocated to each of the four sons of my grandfather, and the distribution was mutually agreed by all the sons but the same was not registered in their name. all 3 sons except my father possessed the houses and now their children (My cousin brothers) are living in those houses. but houses given to my father was occupied long back (1980s) by my two cousins citing emergency which they now refuse to vacate. My father along with us was not staying there but in another city as he left hometown for job. Now the situation is that we are not in possession of any of our ancestral house and our cousins neither pay rent nor vacate. would it be wise to adopt tedious and uncertain long legal battle. how can the house be got vacated as all request and mediation failed.