About Release Deed

After my father's death in 2008, our row-house(in talegaon) is in the name of my mother, elder sister, brother and myself (Youngest sister). Since 2007 I am with my mother - along with my daughter. My father also has a property in our native place (bihar) having almost same valuation as our row-house property in talegaon (Pune). Now we all agree that my brother and mother will do release deed of the row-house property in my and my sister's name. But my sister-in-law (brother's wife) may have an objection. My brother will be coming next month for the release deed process. But we have a doubt whether the Release deed can be cancelled later on by his wife? Whether the release deed remains permanent. My brother is a retired major of indian army. he had a terrific accident before his marriage which was a head injury. he is medically p2 case as in army medical terms and experiences seizures occasionally. but after his accident he worked for 19 years in indian army. he is fit and fine to perform all his activities and did his job perfectly. but on medical grounds can his wife cancel the release deed of the property?