Is it appropriate for the ex-wife's sister to go to her ex-brother-in-law's house?

Whether it is appropriate or not depends on the specific situation and the feelings of all parties. Here are some factors:

1. Kinship: There is a family relationship between the ex-wife's sister and her ex-brother-in-law. They maintain a good relationship, and both sides are willing to keep in touch and interact, so it will be considered appropriate for the ex-wife's sister to go to her ex-husband's house.

2. Feelings after the breakup: The breakup between the ex-wife and the ex-brother-in-law was peaceful and friendly, and both sides had no psychological burden and contradiction, so it is also appropriate for the ex-wife's sister to keep in touch with the ex-brother-in-law.

3. Other family members: We should also consider the feelings of other family members, especially the opinions of ex-wife and ex-brother-in-law. They are dissatisfied or opposed to this, so it is also important to consider their feelings. Therefore, whether it is appropriate for the ex-wife's sister to go to her ex-brother-in-law's house involves family relations and personal circumstances. There is no fixed answer, and it needs to be judged according to the specific situation. The most important thing is to respect everyone's opinions and feelings and communicate openly with relevant parties.