Maternal Grandfather Property Issue

Good day Sir/Madam, I have few questions reagarding my maternal grandfather's property. My grandfather passed away last month. 1) My grandfather has property in Punjab and in Mumbai. He had one son who passed away 5-6 years back. He has 5 daughters. 2) He has named his property for the below persons, a) Daughter-in-laws. b) 2 Grandson & 1 Granddaughter. c) He has one house in Mumbai named under his wifer (my maternal grandmother. His youngest daughter is a divorcee. They were residing in Mumabi for almost 45 years. 2 years back they shifted to Punjab as they wanted his grandson to know about their property. But, after going to Punjab his elder grandson planned to got to New Zealand for studies and started to ask for all the original poperty papers from him. My grandfather gave all the property papers. Now, his grandson's visa was rejected. My grandfather started to ask for the property paper which his grandson started giving excuses that It is with the agent. Wherein all the original papers was with his mother only. Later, after seeing their behaviour and greediness for property he planned for change his power of attorney but unfortunate thing happened and because of his illness he passed away. Now, I just dont want his hard earned money to go in vain as I am sure that my aunty (Maami) and her siblings will ruin his hard earned money. Can you advise, how can we help my grandmother to keep the property safe? Is there anything that can be done like where without my grandfather's daughter's permission or signature is required to sell or purchase any property? Please help. Many thanks.