Mentally Unfit Heir in Property

Greetings to All,

I have another Query related to Property distribution in case of a Mentally Unfit heir.

I have an Uncle from maternal side (technically my mother's real brother) and he is mentally challenged. The property in which he resides (my Maternal Grandfather's Property) is under dispute by his elder brothers who are sane and wants the complete property to be divided among the two of them only, since my mother passed away and one of her brother too and out of the three remaining, the concerned one is mentally unfit.
My mother wanted the property to be distributed in a way that even this concerned brother gets a share of it as he wouldn't have anywhere else to go to and no income to feed his own belly. Right now he is taken care of by my aunt's (mother's cousin sisters) they also reside in this property and if the property is sold out they will also move to somewhere else, obviously leaving the concerned uncle homeless.
I want to ask how is it possible for him to get a fair share in the property because as per the information I am getting from that place the eldest Uncle is planning to take his custody and after the distribution of the property, abandon this brother of his. He is obviously an evil person, I just wish to know how to protect this Uncle of mine as he was close to my mother and protecting him was her wish and I want to safeguard that wish of her.

Thanks in Advance