What is the ruling on a wife remaining in her husband's home, where he lives with his family, and his brother insults religion, does not pray, and abuses her and her family, while her husband takes no stance regarding this?

The husband's brother, who abandons prayer and insults religion, is in grave danger. Insulting religion is an act of disbelief that expels one from the fold of Islam. If he slanders and insults his brother's wife, he is an oppressor. However, the husband does not have the authority to discipline his brother. The wife may refer the matter to the judiciary to claim her rights, but it is better for her to forgive and seek her reward from Allah. The wife should gently advise her husband to counsel his brother and guide him towards the path of goodness.