Probation and share of property

My grandfather has 3 sons and 1 daughter. In his first will, he has written that his 2 ground property will be equally shared by all 4. But after the manipulation of his youngest son, he has changed his will saying that, one ground plot will be given to youngest son and another ground plot with house in it will be shared by elder son and middle son(my father), that is, a. Ground floor of house and half uds of ground to elder son b. Half uds of ground and first floor of house for middle son. The daughter does not want any share. Pleade guide us whether will needs to be probated and whether after probation, the middle son (my father) can make his elder brother sell the house so that he can get his share because right now, the elder son is not willing to settle my father his share of the property.