Sister-in-law suffers from serious mental illness.

This is schizophrenia, which is caused by family pressure. You can see a psychiatrist as soon as possible. At the same time, in this case, it is best to let your brother and sister-in-law live separately from your parents, and then some psychotherapy can cure them. But if this drags on for a long time, it will become more and more serious, so that it will become hopeless and even unable to take care of itself, thus bringing a heavy burden to the family and your brother. Other people's girls are also the pride of parents, that is, your brother loves her, and she has no problem in principle, so she must learn to tolerate and accept. People should not hurt each other, but love each other. It will be very happy to give more love to others! Life depends on looks, and looks can't be eaten. In addition, what matters is whether a person is kind, not how he looks. There are many beautiful women, and you married an aunt. Can you stand it? A family harmony is the most important! Young people will honor the elderly, and the most important thing is that husband and wife are loving and caring! Very sympathetic to your brother! Please don't interfere with your brother's family affairs, too. This is not a sign of love, but an act of ignorance and rudeness! It's really sad to hurt a good youth like this! Advise the family to change their prejudices, besides, your sister-in-law is a member of your family now. She is ill, and your brother is the most seriously injured. I don't think this is what parents want to see, do you? Finally, I wish your sister-in-law a speedy recovery!