Praise be to Allah.
1 – If visits could be made at times when the sister’s husband is not at home, this may help to solve the problem.
2 – Perhaps the visits could be done the other way round, with her family coming to visit her.
3 – There may be something that happened to give rise to doubts in the husband’s mind, or it may be a kind of waswasah.
4 – The length of visits should be referred to custom and to mutual agreement between the spouses. The wife should always be advised to fear Allaah with regard to her husband; she should strive to obey him and to protect the family atmosphere from disintegrating as a result of the hatred caused by each party clinging to his or her point of view concerning the length of visits and so on.