What is the ruling on a wife who refuses to sleep with her husband, does not care for him, and prefers her brother over him?

A wife is not permitted to refuse her husband if he calls her to bed without a valid reason. If she does so, she is disobedient (nashiz), and she can be dealt with according to what the Quran outlines. If her situation does not improve, you may divorce her, or keep her and marry another if you are capable of being just. She is not allowed to go out or travel without your permission, and you must prevent her if there is any suspicion. Her aversion might be due to magic (sihr), in which case ruqyah (Islamic exorcism/healing) is recommended.