Can a registered WIll challenged ?

Hi My grandfather made a registered will to divide his all immovable property into his 3 sons after losing his one son. In fact, uncle-2 has beaten & thrown my uncle-3 from a train to some station during a train journey and took her wife with him. Uncle-3 had no kids. It is clear that it happened with consent of Unlce-3 wife, so my grandfather decided to not give any property to her. Uncle-2 kept her and started advocacy for getting half portion of property. Last year, my grandfather passed away after a long illness. Uncle-2 never turned up to see him or helped him for medicines. Now, he is claiming for half portion of property. My father & 4th uncle, had Tehsildar order(registrar of will) to update the name in all lands as per the will. But Uncle-2 has gone in court now. I just wanted to know, if he can invalidate the will as per any act like Hindu family etc. Basic Info: Hindu Family from UP Grandfather passed in year : 2013 Will regitered : Yes, with 2 witness Matter : 4 sons. All married. 1 son had no kid and beaten/thrown with consent of his wife. still missing. So Grandfather don't wanted to give anything to her & registered a Will to distribute the property into 3 sons. Though his one son is the culprit for throwing another son. Thanks