I would say there's no obligation at all. You never asked to be part of that family in the first place, so you owe them nothing, except maybe appreciation for having brought you up well (if indeed they did).
You may get on famously with your family, so you're happy to support them in any way necessary. But if you don't get on with them, if there's constant tension and conflict and dislike, why should you feel obliged to do anything for them?
I didn't get on with my father, and I didn't get on that well with my mother. So I never felt obliged to them. I barely know my sister and brother in law as they're quite uncommunicative, so again I don't feel obliged to them. And why should they feel obliged to me?
There's still a general expectation that children will look after their elderly parents, but if you don't feel any bond with your parents, or they actively undermine you, why should they expect anything from you?
Those people who strongly dislike their parents but still feel they should support them and look after them are remarkable, but I could never have managed that.
I don't expect anyone to feel obliged to look after me in my dotage (except the NHS of course). If they feel the urge to do so, that's fine.



