Rights to ancestral house

Morning. This is query on behalf of my in-laws. The house we live in belongs to my husband's grandfather, who died in 2011 without a will. His wife, our grandmother, stays with us in this house, and we have been taking care of her all these years. Grandfather had 3 children, of which one has long expired (but his family remains; all of them live separate from us), one lives separately with his family (but has ensured that his son stays with us, but he does not contribute anything to the household expenses, rather wastes money), and the third one (my father-in-law) has been running the house and taking care of the grandmother all these years, largely based on the support extended by his son (my husband) and daughter (my daughter-in-law, married). My in-laws have been living in this house since 30 years now, we have been paying all bills, and managing all expenses. There is no will yet, though. What are our rights on this house? We do not wish to give up because we have long invested in this house. Also, this house, being located in a prime location, and grandmother's jewelry has long been a thorn in the eyes of the other 2 families. Can you help with an answer?