I live in the same town as my in laws but far away from any of my own family.
We see my in laws every now and again for a quick visit and they have babysat maybe three times for my 16 month old, just for brief periods not all day or overnight or anything like that yet.
We once asked if they could take care of DS one day because his usual carer was sick and we both had to go to work (knew both DH's parents weren't working that day). They did look after him but made the point that we can't expect them to provide daycare on their days off as they want days off to themselves. Fair enough.
On the other hand they have their daughter's two kids who are slightly older overnight to give her a break about once a fortnight and often take them on outings as well. We once all went away for the weekend and SIL would go take naps while in laws did all the care, prepared all meals for her kids etc.
I know they think she needs a lot more help than us as she is a single mother, not working, very little money and has had lots of challenges with her ex, the father of the kids who doesn't help much, although he does have every second weekend with them.
So I do get why they help her a lot more but I still feel a little put out and worry that the difference in attention the grandkids get might become noticeable to them when they get older.