How do you let go of resentment, especially towards family?

The best way for this is the hadith of the prophet sallallahu alaihi wasallam, the hadith collected in Sahih Muslim where he said that have mercy on others and Allah will have mercy on you, forgive others and Allah will forgive you. And this is the most important aspect in our lives, the forgiveness of Allah subhanahu wa ta'ala. So if you keep reminding yourself that you know the most important thing is that I'm doing this, I'm forgiving others, I'm having mercy on others, I'm overlooking the mistakes of others because I want Allah's forgiveness, and inshallah that will make it easier for you.