I will be the lone dissenter who says that yes, Grandparents are obligated to help in some way.
I don't understand this mentality of "Our little nuclear family is an island. We don't need anything from anyone. And when our youngest turns 18, that's the end of our responsibilities.".
Raising the next generation is hard and effects multiple generations. Grandparents are not just kindly observers from afar... they could be an integral part of the support structure that will benefit their children and grandchildren.
Love is more than a feeling. It's an action and it doesn't have term limits.
The problem with this feeling that being on your own is bad, etc is...what happens if all the grands go away?
I joked in my last post, but really, the one grandparent my son would have had who would have probably moved here to be around my son, who would have moved heaven and earth to help us with all sorts of things...died. Before I even met DH.
What do I have left? Crazy father who promised a visit last summer (never showed up), bizarre MIL. FIL was generous and kind, but he stole from his own wife to have the money to be generous, and then he died.
We're not on our own by choice. My MIL watched our son once...she had some random visitor come by who freaked out DS. He won't stay with her again, though he loves visiting her, b/c he's weirded out by the person that came by. We've watched MIL hit her beloved granddaughters, and that's with us around...because of that, DS was 4 when we left him with her, so we would know if she had hit him (and would have ended any relationship with her if she had, which she knows). My father, who knows what he would teach DS? He was a weird parent to all 5 of his kids, and when we visited them when DS was 3, he used the most vile words about his wife, in front of DS, until I made him shush. etc etc.
If I had expected or planned to rely on family for help...I would have been sorely disappointed. I did have wonderful expectations of my mom as a grandma...
But then we've been surprised from the most unlikely people...my blissfully childfree brother and sister in law! They won't watch DS until he's 10 or so, but they've been lovely and generous gift-giving people towards him. And are always up for us to visit them. I would NEVER have expected that! SIL has told us that she plans to pay for DS's college education (and her sister's daughter's as well), even. Astonishing.