Often times children and teens pick up very negative speaking patterns from their school environment, media input, and people around them. Negative self talk and phases like “I’m so stupid”, or “I can’t do this”, are just overlooked.
That also goes for fighting and negative speech with brothers and sisters is usually just considered “sibling rivalry“.
However words have a tremendous amount of power to shape a child’s life and affect on the peers that they speak to. How much trauma or negative memories are you still dealing with from words that were said to you when you were young?
Don’t look past your child’s negative words. Teach them words of self-worth and affirmation and have a no bullying/negativity tolerance with your child teasing their siblings or friends.