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 husband of your wife deserves only one-fourth of the inheritance since his wife has a child; Allaah Says (what means): {But if they have a child, for you is one fourth of what they leave, after any bequest they [may have] made or debt.}[Quran 4:12]
However, he has no right to prevent your wife from her share in the inheritance and it is permissible for her to demand her share from her father and if he refuses, it is permissible for her to take the matter to the Islamic court in order to ask for her right. This is not considered as being undutiful to her father. Al-Bukhari reported that Abu Yazeed Ma’n Ibn Yazeed As-Sulami said: “My father Yazeed set aside some Dinars (gold coins) for charity and gave them to a man in the mosque (so that he would give them to the poor) but I went to that man and took them and brought them to my father.” Then my father said: “I swear by Allaah! I did not intend to give them to you.” Therefore, I took the case to the Prophet . Then, the Prophet said: “O Yazeed! You have been rewarded for what you intended; and O Ma’n! You are entitled to what you have taken.”” [Al-Bukhari]
Ibn Hajar said: “This is evidence that it is permissible for a father and his son to resort to arbitration, and that this, by itself, is not considered as cutting ties with kinship.”
For more benefit, please refer to Fatwa 124046.
Allaah Knows best.