Cancellation of gift deed under senior citizen act 2007

mother had two sons and she gifted her property i.e, 1/2 share in a house to each son with a condition that after her death both sons will get full rights on that property and she kept her rights to enjoy the rents of her property by her .This gift registration has done in 1999 i.e., before senior citizens welfare and maintainance act 2007 ..all the parties of the registered gift was not in elder son decided to take the advantage by cancellation of gift deed by her mother and trying to take whole house by showing cause that younger brother is not taking care of her. actually elder son not allowing younger son to meet and serve their mother and the rents are taking by elder son only . mother is residing with elder son..younger son also sent notice to his brother to allow him to see the welfare of her mother though gift registration is not made on the condition that the sons will take care of her mother can cancel the gift registration ..please give clarity to my question sir