Not sure about where you live, but where I am (UK) as far as I know it isn’t the legal responsibility of children to take care of elderly relatives, not even parents.
As an aside, I think it’s incredibly dumb to have kids for this purpose, to be honest - having worked in a nursing home for nearly 20 years I can tell you several ways this can backfire, and it wouldn’t be an exhaustive list either. Even if someone is willing and has a good relationship with relative in question, it doesn’t always mean they’re able to provide appropriate care, for a start.