Cancellation Of Family Partition Deed

sisters son is trying to cancel brothers registered family partition Deed of ansisterial property which was signed 13 years ago between brother sister and his family  and the property rights is transfered to brother.  sister passed away in 2011 , now his son is trying to cancel the registered partition deed saying that his mother has signed the deed for very less value . he is claiming that it is his ansisterial property and he was major when his mother signed the deed.  value matters in Family partition deed?  what would be the advice for sisters son?  does one of the party of two who signed the deed can cancel the deed ? sister son is claiming that my mother signed the deed for only for cash not for land so the deed is void  is he right? he is saying that Not a cent of land is given for my mother only cash is given  does his argument has any validity? sister son is also saying that he will bring stay order and will not allow brother to buy /sell or even take loan against land