Do you believe grandparents are obligated to help babysit their grandchildren on a regular basis if their children are in a situation where they need it or can’t afford other babysitter?

I want honest answers and those who are willing to comment please do! My ex and I have been arguing about this for years now. He thinks grandparents are obligated no matter what to watch their grandchildren and I feel differently. I don’t think anyone, not even family, should be OBLIGATED to help with the kids except for the parents. However, I think if families are really working together and being a loving family that things should be worked out if certain family members need the help but it also depends on why the grandparents can’t help. In my case, my parents can’t help very often because they can’t afford to take time off work. But he doesn’t care and thinks that’s a bs excuse.