I am going to interfere with my brother's family because my brother got my sister in law pregnant.
Why are you going to interfere in your brother and sister in law's marital life?
Because I'm tired of him always ruining things. I'm blaming him for many bad things in my life.
The marital decisions of your brother and sister in law are none of your business. Mind your own business and be concerned about your own decisions or your brother and rest of the family will be angry at your interference.
There is a war going on in my family. I'm attacking him back.
I'm not even quite sure how you could interfere in your brother's wife's pregnancy, but you really should stay out of it. If your relationship with him is so bad that you're warring, it's best to take a step back and let things calm down.