Right on ancestral house

It becomes your grandfther's property hence upon his death the property shall devolve on all his legal heirs, therefore the grandchildren cannot claim any share in it a right at least not during the lifetime of their respective parents entiltled for a share in that property

Thank you for your reply Sir. I have another question. Out of the 6 children if one of the son stays in the house for a long time 40 plus years. Does he have the legal right on the house?

He has been living in that house for a very long time, but he cannot occupy it as the remaining heirs have an equal share in the property.

In the given situation the legal heirs of your grandfather have to initiate proper legal action to file a suit fior partition to claim their rightful share in the property with separate possession, the person living in the property for over four decades may have to vacate  and deliver vcant possession as per court order once the case is disposed.