So my DSis is the golden child and her children are the golden grandchildren. I realised a long time ago that I was basically surplus to requirements and moved a long way away.
Relations with my family are civilised: I visit about once a year (they never visit me) and speak to my parents on the phone about once a week. My parents are quite pleasant to me on the phone when my sister is not around, but when I visit she is always around and they tend to follow her lead in putting me down.
My parents and my sister are very close: they see each other every day. My parents looked after my sisters kids while she worked and mostly had them at weekends too so that she could go out. They have never babysat my kids. They've never helped me at all. They go on holiday together and have family parties without inviting me. I never go for Christmas after one miserable time when my kids were small and were basically ignored in favour of DSis's kids. I've learned to not let it bother me.
Last week my sister phoned, which she hasn't done for about a year. Generally she only phones me when she wants something, so I was wary but she was chatty and nice. Then she started saying stuff about advising her grown up kids not to give their lives up to support her in the way she has given up her life to support our parents. She said she'd been self reflecting and felt she needs to step back a bit from our parents, that she's carried them for a long time.
Basically, the way I see it is that my parents have run around after her for years and more or less raised her kids for her and now they are a bit older, and need a bit of help themselves, she's laying the groundwork for passing that responsibility on to me.
Mostly I'm just irritated that she thinks I'd be stupid enough to fall for it.