Need the opinion on property ownership

Hi Sir,

I have ancestors home which is registered with the name of my grandmother & others(Assuming, others must be her sons as daughters are already given NOC) after my grandfather death. Now my grandmother is expired as well. Is there any possibilities that one son can take the NOC letter from daughters & without informing to a younger brother, change the ownership of the house?

if yes then how can we prevent him? If he takes loan on house & not planning to pay back then what will happened?