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.
You should supplicate Allaah as much as possible to reconcile their hearts and take away their estrangement. You should not despair in supplicating as Allaah is able to do all things.
It is best to find and try to eliminate the causes of this misunderstanding, and to seek the help of righteous people in this regard. Bringing adversaries together is one of the best acts of worship; Allaah says (what means): {No good is there in much of their private conversation, except for those who enjoin charity or that which is right or conciliation between people. And whoever does that seeking means to the approval of Allaah — then We are going to give him a great reward.} [Quran 4:114]
Abu Ad-Dardaa’ narrated that the Prophet, sallallaahu ‘alayhi wa sallam, said: “Should I not tell you what has a higher degree than fasting, prayer and charity?” They said: “Yes.” He, sallallaahu ‘alayhi wa sallam, said: “It is to reconcile differences, for discord is the shaver (i.e. destructive to faith)” [Abu Daawood and At-Tirmithi]
Also, you should remind them of the ties of kinship between them, which they are obliged to maintain and are forbidden from severing, hoping that Allaah would guide them to His straight path.
On the other hand, you should be wise in dealing with the matter and give both your husband and your parents their rights. In case there is conflict between those two rights, then the right of your husband takes priority. Shaykh Al-Islam Ibn Taymiyyah said: “If a woman gets married, her husband has more rights over her than her parents, and she is more obliged to obey her husband than her parents.”
For more benefit, please refer to Fatwa 107622.
Allaah Knows best.