You have to accept it i'm afraid. My DH had it out with his dad once and his dad just said that's how he was.
When we accepted that my and his families played favourites and moved on from that life was easier.
Shit for the dc tho,my eldest barely speaks to my parents and realised a long time ago that my brothers dc were the favourites.
DH is always saying that it's their loss but i don't agree. They don't give a fuck and my dc do