Probate of will

My grandfather(mother’s father) expired due to covid 19 on 19 may 2021, My grandfather and his elder brother are residents of one bungalow which is like a duplex and is divided between them equally. My mother is only child of these two families. But she is real daughter of the younger brother and elder brother adopted her verbally and his name is used in all legal documents. As the elder one was not having a child. Both of them (nanu’s) got married again after my birth as both my Grandmother’s (nani’s) expired due to cancer and brain tumour. After that in 2012 both my nanu’s (grandfathers) decided To make a will in favour of my mother (all the immovable properties)to her and movable property in favour of their second wives. They both don’t have any children from there second wedlock . Now my grandfather (younger one) expired this may. And my mother wants to probate half of the share and she has the authorised will with her but not the property papers. As the elder father is still alive and both second wives are still alive. How can my mother probate the will.