Sharing of blame for everything is one of the main causes of the rift between my brother and I.
My brother is 3 years younger than I, and as the oldest, I was held responsible for everything. If he refused to do his part of chores, I got punished as well. If he misbehaved, I got punished as well. He enjoyed this. If I did well, he shared the award with me. He learned that he could easily get my privileges taken away and still reap the rewards himself of my good grades, my doing chores, etc. One of the main things we got punished for is fighting. I stopped fighting with him and he would just keep on taunting and attacking. He would increase his attack until I had to respond. He used weapons such as an aluminum baseball bat or a metal ashtray stand to attack me from behind. Ignore that long, even from a 5 year old, you are dead. If I told, it only increased my own punishment, so I learned to take as much as I could. He god good at taunting me through blockaded doors. Blockaded because he would do his best to knock them in if I just locked them.
If I failed to act as his servant, he would either make up something to get me in trouble or do something himself. Punishment did not seem to bother him at all, but it tore me up. I hated being punished, especially for what I did not do. I grew depressed. As he grew up the lesson he took from it is that it was ok to punish me for things he did or for no reason at all, and there was no motive for him not to punish me directly as well.
Once whem my parents went out for the evening, I was 16, I tried to eat part of the dinner that she had left for us, he beat me bloody. He had decided that I was too fat and did not need to eat. I escaped into the street eventually and some kind people took me in and called the police. When the police came and got my parents to come home, I, again, was the one in trouble because I could have ruined my father’s career. I stayed home from school the next day because my left eye was swollen shut and I was too sore to walk. That was not the only time something like that happened, but it was the only time I ran outside. I learned again that I had to just take his abuse. I grew more depressed.
I moved out as soon as I could after graduation. If I visited home the abuse continued. Last time I tried to visit my parents, I was 21, he broke my nose and beat me hard enough to bruise bones. The doctor was surprised that nothing was broken.
I no longer speak to him. I will only attend family functions if he is not present. I find that with no active abuse in my life, I don’t get depressed anymore.
You may get lucky, or you may just encourage parasitic behavior. I hope you have better luck than my parents had.