how to transfer the property after death of father(allottee) & mother

I am living in ancestral kothi in delhi (3 floors). My father (expired in 2013) made the registered will jointly with my mother allocating all three floors to three brothers and nothing to sister if we continue to live there. However in case of selling the kothi then 10% sale proceed to sister rest equally divided among three brothers. My mother expired in 2019 (property was mutated in her name) How to go about registering/mutating the property in brothers name either jointly or partition wise. Which is better as far as registration amount is concerned. Is probating will necessary. As per will three brothers are allowed to rebuild the property also. Can we make four floors (as allowed) and give one floor to builder.