Second: make way as much as possible. Maybe your brother is grumpy, and I am a grumpy person, so I know it's hard to change. The more I asked him to change, the less he changed, but the more grumpy he became. Besides, people who are generally grumpy are more proud. Some of them know that they are wrong. You should give him a chance to step down.
Third: don't speak ill of your brother in front of your parents, such as poor grades, but also tell your parents. Don't compare you two, compare your strengths with your brother's weaknesses. My brother won't like it.
Fourth: get to know him and understand his thoughts. Maybe you think this sentence is normal for you, but it is another matter in your brother's psychology, so it is easy to produce contradictions.
Please refer to.