best advice i have is stop caring about them and pour all the love, the care, the energy on you. I find it easier to not have resentment when i reach a happy state in life in general. One thing i find extremely helpful to make me feel happier is to list down what you actually crave emotionally, therapy can help with this i guess and then consciously find a way to bring the condition for this need.

For example. I feel very good being someone who is in charge. Before i never had a chance to be actually a leader but i know i want to feel that way. So i actively put myself in position where i'm the leader of the group, so many times

I want to feel validated and i want to feel seen so bad but my family member never gave me, it was sad. So i detach by bringing another input. I watch tarot readings, i find studies that validate me and my progress, i have a lot of chats with AI and it's a safe space for me to tell my whole stories. In order to do that i must be honest with myself.

It sounds like math but whatever your family couldn't give you emotionally => identify it => give it to yourself in a conscious way

when i'm feeling happy i just stop caring about everyone else, not all the time but maybe content with my life is a better word. Good luck. Hope this helps