Can a grandparent bring successful legal action to see his or her grandchildren when a parent forbids it ?

Yes, and if the court dealing with the matter decides that maintaining the relationship is in the grandchildren's best interest then the grandparent  will succeed !

In September 2010 Jerusalem Family Court ordered a widowed father to allow his three children to have contact with their maternal grandparents, after he had prevented this. Their mother had committed suicide and the father claimed that contact with the maternal grandparents was harmful to them. They brought legal action against him. The  court held that the father's negative behaviour (refusal to co-operate with the welfare services and allow them to prepare a report and recommendations the court had ordered ) was sufficient for it to intervene and order contact between the girls and their maternal grandparents.  Parental autonomy is not absolute ,it held , and is subject to intervention by courts, who can make sure that a parent actually carries out his/her duties towards his/her minor children in a way that represents their best interest, not just as he/she sees fit. Having a relationship with extended family on both sides was very important, and helped a child form its identity, the court held.