1.The property as per will is transferred after the demise of the executor. How come your grandmother has executed keeping one part with her? If she has not willed 1/3rd portition of her property then all her children will have equal share on that portion of the property after her demise,
2.The property of your grandfather will be equally owned by all his legal heirs after his demise intestate,
3. You have not mentioned whether your grand parents are still aklive or not,
4. If they have demised, then all the legal heirs of your grand parents should make settlement deed for the property of your grand faher and the above unwilled portion of property of your grand mother,
5. After executing and registering the above settlement deed, the legal heirs cum settlees can mutate their names in their respective portion of the properties.