Is the mother entitled to marry off her 18-year-old daughter to her husband's son despite the objection of the father residing in America? And what is the fatwa of Imam Al-Shafi'i that permits this? Is it Islamically permissible for the daughter to live with her mother, her stepfather, and his young adult sons in the same house before marriage?

The person with the most right to be the wali (guardian) for a woman's marriage is her father. It is not permissible, according to Islamic law, for anyone to marry off his daughter except with his authorization. The claim that the Shafi'i madhhab permits marrying off a girl who has reached eighteen years of age against her father's will is incorrect.

The father is advised to respond to the request for his daughter's speedy marriage and to appoint his brother or someone else to conduct the marriage contract, in order to protect her honor and preserve her dignity, especially since he has approved of the suitor. Delaying the contract for the sake of his presence is a far greater detriment than appointing someone to perform it.

Regarding the daughter living with her mother in a house with her stepfather's adult sons: if the entrances and facilities of the house are shared, then it is forbidden, because they are not her mahrams (unmarriageable kin) unless fosterage during the first two years of life can be proven. If her living quarters are independent with their own facilities, there is no objection, provided that fitna (temptation/strife) is safe. It is forbidden for the daughter's mother and her husband to incite the daughter to disobey her father.