All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
It is incumbent on the grandchildren to uphold the ties of kinship with their grandparents because they are among the kindred with whom it is obligatory to maintain the ties of kinship, and it is prohibited to cut them off. It is impermissible for the parents to prevent their children from upholding the ties of kinship with their grandparents; such an act constitutes enjoining evil and forbidding good, and therefore, it is prohibited to obey them in this regard. The Prophet said: “There should be no obedience to a created being in what constitutes disobedience to Allah, The Exalted.” [Ahmad] The neglect on part of the grandparents in maintaining the ties of kinship with their grandchildren does not justify cutting relations with them on part of the grandchildren, especially given that the position and status of a grandparent is like that of the parent; and therefore, it is obligatory to show dutifulness and kindness towards grandparents.
If there is some kind of misunderstanding between the parents and grandparents, the parents have no right to prevent the grandchildren from upholding the ties of kinship with their grandparents, and reconciliation should be sought. It should be noted that it is obligatory on a child to show dutifulness and kindness towards his parents, even if they wrong their child and offend him.
Allah Knows best.