Why does Liam claim this is his fault? He never forced his brother to do this, hate this chapter.
Your brother with a negative IQ score decides to get some people killed MC: "This is my fault!" Bruh what?
Well, if you consider this carefully.
1. Why MC big bro use this desperate method? Because he feel that his position being threaten by MC
2. Why he feel that his position being threaten by MC? Because MC has recognized by the crown and has been granted title of baron while he himself is not have any notable achievement and if his dad fail to achieve anything he will become commoner by the law.
3. How does MC gain an achievement and got recognized by the crown? It's because he is so proficient in using magic.
From all of the above, its reasonable that MC is considered himself to be at fault and source of his big bro desperation.
Please note that I agree that it isn't MC fault that his big bro become like this, I just wanna point on why MC think this is all his fault.