Is it permissible for a girl adopted by the family of the questioner's husband to remove her hijab in front of her husband's paternal uncle (the husband's father), the questioner's husband, and his adult brothers, knowing that she has reached puberty and was raised by the husband's family?

This girl is a stranger to the men of the family she grew up with, unless the mother of the family or one of her daughters breastfed her before she completed two years of age, in which case she would become a mahram to them through suckling. Mere adoption and upbringing do not make her a mahram to them, so it is not permissible for her to uncover her hijab in front of them or to be alone with any of them. Adoption, in the sense of the girl being attributed to the family in inheritance and other matters, is among the practices of Jahiliyyah (the pre-Islamic era of ignorance) that Islam abolished. However, embracing foundlings and raising them carries a great reward.