Grandparents vary as much as parents and children do.
My ex MIL was toxic, i estranged her completely in 1979 and never saw her again. Nor did my kids, until they were in their 30’s, and once was enough for them.
Courts or no courts, hell would have frozen over before I had complied with her seeing them. To be clear, my ex husband (her son) felt the same way as me.
On the other hand, my parents were wonderful GPs, and even if I had fallen out with them, there is no way I would have kept the children from them. They just all loved each other to bits.
Children might have some rights, but parents, ultimately, need to have the final say. So, if the parents don’t want contact between GPs and GCs, for whatever reason, that’s the way it needs to be. No courts, no trying to see them, nothing.
Children can’t possibly make decisions about seeing someone, as they may not know the background to the problems.
The Family Court system is unreliable anyway - many fathers struggle to see their children, despite court orders saying they can. The mothers often block them.