All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
The jurists stated that if a woman becomes married, her husband has greater right over her than her parents and her obedience to him comes in priority over her obedience to her parents. Therefore, if your husband insists on moving to another accommodation, you are obligated to move with him especially that he does not prevent you from visiting your mother. We advise you to try to please your mother so that she will be pleased with you.
Moreover, you should endeavor to reconcile between your family and the husband of your sister; Allaah Says (what means): {…and settlement is best. And present in [human] souls is stinginess. But if you do good and fear Allaah — then indeed Allaah is ever, with what you do, Acquainted.}[Quran 4:128]
Besides, Abu Ad-Dardaa’ narrated that the Prophet said: “Shall I not inform you about what is better than the degree of fasting, praying and giving charity….? It is reconciling the conflicting parties, for conflicts are like shaving blades (i.e. it eradicates religion).” [At-Tirmithi, Abu Daawood and Ahmad]
You should also remind them that having a good relationship with the in-laws is required, and it has its good effects in this world and in the Hereafter. On the other hand, bad relationship has bad consequences in this world and the Hereafter.
Finally, it should be noted that if the brother of your husband insults your mother, then he is wrong. Because if he is not good to her he should at least not harm her or mistreats her.
Allaah Knows best.