The implication that my brother got married behind my sister's back

The moral is that the bride's family will always be the bride's protector.

My brother is married behind my sister's back, and my sister's family can remind her that my sister won't be bullied if my brother is in charge and I have a backer.

When a girl gets married, it means leaving one family to live in another, so getting married is called a "big event", which is very grand. Since ancient times, there has been a saying that "my sister goes out to the back of the boudoir, and my sister goes back to her mother's house to pick her up."