Is it okay to hit my brothers or sisters if they hit me first?
Here's the answer:
Jesus said to turn the other cheek.
It's wrong to hit someone back just because they hit you—that's called revenge, and it's a sin. You should always try to walk away and stop a fight, especially with your own family. If we can learn to get along with our family, we'll probably be able to get along with nearly anyone else we meet! Try to get your brother or sister to talk about the problem with you. If that doesn't work, get a parent's or other adult's help.
God wants us to show other people love instead of hate. Jesus said that if someone hits you, you should turn the other cheek for them to hit. That doesn't mean you have to let someone beat you up, but it does mean that you should show kindness to those who try to hurt you. When people were beating Jesus and nailing Him to a cross, Jesus didn't get mad at them. Instead, He prayed "Father, forgive them. They don't know what they are doing" (Luke 23:34). The people who were hurting Jesus didn't know that Jesus was God the Son who had come to earth to take the punishment for sinners by dying on the cross. Do you know and trust Jesus? You can read more about that here.
"But here is what I tell you. Do not fight against an evil person. Suppose someone hits you on your right cheek. Turn your other cheek to him also" (Matthew 5:39).
"Don't pay back evil with evil. Be careful to do what everyone thinks is right. If possible, live in peace with everyone. Do that as much as you can. My friends, don't try to get even. Leave room for God to show his anger. It is written, 'I am the One who judges people. I will pay them back,' says the Lord. Do just the opposite. Scripture says, 'If your enemies are hungry, give them food to eat. If they are thirsty, give them something to drink. By doing those things, you will pile up burning coals on their heads.' Don't let evil overcome you. Overcome evil by doing good" (Romans 12:17–21).