Well 'only siblings favoritism' isn't just an 'only' imo. Especially if you're the family scapegoat. If it's implied they are perfect and you, can do nothing right...that can fuck you up for life.
You can be left...indecisive, fearing that any decision you do make will be wrong, so incapable of acting. Which in turn, can make you feel like you are lazy. And, may feed that narrative they have or that you fear they have of you.
It can cause you to feel like a failure every time you make a wrong choice. Or even, when you do act and it goes wrong, to blame yourself irregardless of how it went wrong.
It can make you date toxic people because you fall for the initial lovebombing because you just want someone to love you like that. Like you're their priority. Or potentially, to date cold asked people like your parents because that's a familiar dynamic to you.
It can leave you a desperate people pleaser. Always needing to 'earn' being liked. Even with people potentially, who are not nice human beings.
Or it can leave you isolating from the world. Because you've been taught that you aren't special and people don't care about you so you can only rely on yourself. That if you go out into the world you will be hurt and ignored.
So it's not only favoritism. It's potentially treatment that shaped your whole life. Left you feeling 'not enough'. Thus inviting other bad people to treat you similarly.
And if this is the case, no wonder you are angry. By forcing yourself to see them, you are essentially carrying out self harm. Your body is rebelling with rage because you know, you KNOW you ARE good enough. But every time you see them it's like you're telling yourself they are right and you aren't all over again. It's not healthy.
It's time to choose you.