I understand
my parents were well off when I was younger. When I had my first child, they made me homeless. They threw me out at 5 months pregnant. I was sofa surfing. They continued to bicker in a 4 bed Victorian Semi. They didn't like me to stay too long with the baby and certainly I never slept under that roof again.
My dad has had 2 affairs, left mum and then the next one, and now lives in a bedsit. My mum was left with the 4 bed semi with no mortgage yet somehow managed to poorly manage her finances until she had it remortgaged to the hilt and it had to go. Then the smaller house she bought had to go - to may brother and sister who, although adults, still lived there. Now they own it and she lives for free in the smallest room.
And like you, I'm really resentful that I seem to be expected to do more for her at the age of 38 than she ever did for me when she was 38. I sit with her in a and e all day. I take her on holiday.
She avoided me and the kids like the bloody plague when they were small and I desperately needed her. Dad has taken ds1 to the park once but as ds1 has adhd and asd, he opened the car door while it was still moving and nearly got killed (why no childlock???) so he never took either of them again.
And like another poster said, the absence of support they left me with was filled with other things. Friends, trips, hobbies. Now they want me, now I have learned to do everything myself without any help and am actually more competant at managing my finances than they ever have been, now I never need a lift because I can drive, now I never need a babysitter because the kids are teens, NOW they want me to entertain and support them, somehow juggling both of their wants separately.
I'm not surprised you're resentful. I'm resentful. I cannot help thinking that people born postwar have grown up quite selfish and VERY grabby.