Gradfather died with a Will to share property to Minor grand children - But minors were not alloted

Legal Issue Regarding: Background of Legal issue - My Grandfather had 4 sons, before his death he created a WILL at around 1988 March Month, in the WILL he clearly stated that he is dividing his property by 1/5(he included his 4 sons and 1 share he mentioned as his share of property in the WILL). In the WILL he clearly mentioned that 1 portion of the property (His portion) has to go to grandchildren and mentioned the names of the grand children who can get the property. All the Grand children were minor at the time of my Grandfather death. After Grandfather death in 1989 - all 4 sons divided the property but mentioned in the division document that they are not including the share of grandchildren mentioning that it is not legal to provide such split to grand children and excluded the minor children for the property split. The whole property was split in to 4 and divided by the sons alone. Some more points for reference: The family is Hindu family, The property is all earned and acquired by my grandfather and it is NOT an Inherited property from his father.(Self acquired property). Grand father created WILL during 1988. Grand Father death during 1989. The property was split by the sons during 1989. Only 4 Grand children’s are mentioned in the WILL by the Grand father. Questions: 1) Can Grand Father split his Self Acquired property in to 5 division(4 for his sons and 1 for him)? 2) Can Grand Father allocate his Share of the Property and allocate it to Minor grand child in the WILL is it legal? 3) When dividing the property the sons of grandfather only divided in to 4 mentioned in the division document that allocation of property share by grand father to grand children is illegal? is this act correct by the sons? 4) Can Grand sons claim the property now in 2020? 5) Can grand children mention that the division of property was not legal? can they mention that the property split agreement was illegal? if so how to approach the court? on what count the case has to be started?