What is the ruling regarding my actions of hitting my sister and brother, and what is the ruling regarding my hitting someone who previously assaulted me?

It is not permissible to respond to insults with blows. As for someone who intends to strike you, he is an aggressor (ṣāʾil), and it is permissible to repel him with the lightest means. It is not permissible to repel him with blows if he can be repelled with something less. As for striking back at someone who struck you, in retaliation (qiṣāṣ), some scholars have permitted it. To repent from striking others unjustly, please refer to Fatwa No. 145924.