Is a father entitled to take custody of his daughter and raise her himself, given his fear of her growing up in the strange house of her grandmother's husband?

The mother has the primary right to custody of the child as long as she does not remarry. If she remarries or is deemed unfit for custody, then custody transfers to the child's maternal grandmother.

If the custodian marries a person who is a stranger to the child in custody, her custody right is forfeited and transfers to the next in line. This would be the father according to the Hanbalis, or the paternal grandmother according to the Hanafis and Shafi'is.

Upon the girl reaching seven years of age, her custody transfers to her father in the madhhab of Imam Ahmad. According to the Hanafis, the fatwa is that it transfers to him upon her reaching nine years of age, and according to the Shafi'is, she is given a choice after seven years.

The conclusion is that the maternal grandmother has no right to custody here due to her marriage to a stranger, and custody transfers to the father or the paternal grandmother. If the girl reaches seven years of age, she will be with the father, or given a choice, as mentioned.