Is the husband considered unjust to his wife if he prevents her from visiting her family regularly, knowing that there was a prior agreement to allocate a specific day weekly for the visit, and she wishes to spend more time with her siblings who are coming from another governorate?

You are not at fault for preventing your wife from visiting her family in the aforementioned situation, nor are you considered unjust as long as you permit her to visit them once a week. It is not permissible for her to go to them without your permission, even for a short period or due to the arrival of her brothers. Whenever you can grant her permission without harm, do so, as this fosters affection and improves marital relations.