Will probate

Hi, I live overseas. However, recently my grandfather passed away & he has a son & a daughter who inherent a property which consist of 3 floors. The Son lives in the property & the daughter has occupied the top floor. The SON has a copy of registered will that we got made few years prior to his death. The will advises that the daughter would be entitled to only 3rd floor of the property. The ground , First & roof rights would be entitled to his SON. Since then we have approached the other party and made a reasonable offer to them to avoid going through court & probate the WILL. The house is over 40 years old and is in bad condition. It requires a new construction. we have been approached by various builder who suggested he will keep 1 floor & build us the house. we have offered the other party 50% cash from the money we receive from builder & one floor along with roof we have offered the other party 50% cash if we knock it down and give it to a builder & roof rights but the other party keeps changing their mind & keep asking for more. We have agreed to give them more than what it stipulates in the will. I don't live in India i am not sure about the Indian laws. However, any suggestions if we go to court to get the WILL probate will it give us any justice? The other party is not willing to re construct the house & is not ready to come to negotiate in any terms.Also i am not sure if they have faked any WILL in order to gain more rights to the property. any suggestions would be very helpful.