How do you deal with self absorbed family members?

I'm about to go crazy. My sister put something up online that's VERY personal about myself online because I didn't do a very small favor for her. My dad is even worse, we cant have a conversation that's not about him and what he accomplished. My brother is just like the two of them combined in one but worse, he thinks since he is older than me by 3 years I have to bend over backwards and do whatever he ask me to do. Only people that are not self absorbed are my mom and older brother by 5 years. What do you do with self absorbs people? I need ways to calm down and deal with them before I do things and say things I will later regret