Am I sinful for refusing to host my wife's family in my house, fearing they might harm me or my wife through magic, especially since they are trying to separate us and mistreat us?

The fundamental principle is that a husband is not permitted to prevent his wife's parents and relatives from visiting her in her home, unless he fears harm from them. If the husband fears they might cause him harm or separate him from his wife, then he is permitted to prevent them. However, it is stipulated that this fear must be based on a genuine reason. The Maliki school of thought holds that he should not prevent her parents, in particular, from visiting her, even if they are ill-mannered; instead, a trustworthy woman should accompany them during their visit.