I understand the jealousy, the hurt at the injustice.
I'm the eldest of 3 my mum never did any childcare of dd, I paid for nursery and wraparound care. I was a Lp from dd was 2 I got NO support from my parents at all. Exs parents probably would have but they were older parents and therefore much older grandparents (they're nearer my grandparents age than my parents) so they weren't physically up to it, even an hour exhausted them and that was with me there!
My brother had some support from my parents when he was a Lp for a short while. His late ex's parents did more though.
My sister though, who is very much mum's gc, has had and continues to get ENDLESS support of EVERY kind!
Dd is an adult now (still trying to wrap my head round that one
) but it still hurts.
And worse...it hurts dd because she sees how her cousins are favoured. She has a limited relationship with her dads parents and honestly not much more of one with mine. Its heartbreaking.
But, all that said yabu. Because it's not within your choices, it's not for you to say they can or can't do it.
It's hard, but you have to find a way to set it aside.