Ruling on a woman uncovering her hair in front of her mahrams

The question: This is a letter we received from the sender, Awad Rad al-Harthy, from Maysam in the land of Bani al-Harith, the village of al-Mukhald. He says in his letter: Peace be upon you, and Allah’s mercy and blessings.
And after that:
I inform you that I am one of the listeners to your noble program, which has resolved many problems and illuminated the path for many people. May Allah preserve it and preserve those who work on it, and grant them goodness and reward. I have written this letter to you, including some questions, hoping that you will present them to His Eminence Shaykh Abd al-Aziz ibn Abd Allah ibn Baz, may Allah reward him and guide his steps. Amen.
First question: Is it permissible for a married woman to wear light clothing, such as a shilbah, or to uncover the hair of her head while sitting with her father, her brothers, or her paternal uncle? Please inform us, may Allah guide you?
Answer: A woman should be careful to protect her body and to guard her points of attraction and preserve them, even from her mahrams, out of fear of fitnah (trial or discord). However, there is no harm if her hair, her arm, or part of her leg is visible to her mahram, such as her father, her brother, her paternal uncle, or the like. However, if she is modest and covers her hair, arms, and legs from her mahrams, that is a matter of modesty and caution against some mahrams from whom evil may be feared. This is because some mahrams are open sinners and pose a danger. If she is modest and covers herself in the presence of her mahrams, revealing only her face and hands, or feet, for example, that is better, safer, and further removes her from danger. This is because the evil of some mahrams is feared due to their open sinfulness, deviation, or the disbelief of some of them—there is no power or strength except with Allah. However, it is permissible for a mahram to look at her hair, her leg, for example, and her arm, just as he looks at her face and hands. But if she is modest and covers these things, revealing only the face and hands, or the feet, for example, that is better for her and safer, out of fear of some mahrams who do not have enough faith and mindfulness of Allah to restrain them from evil. This is what is recommended, especially if a mahram, such as her brother or paternal uncle, is alone with her; for modesty in this situation is more appropriate, better, and safer. Yes.
The presenter: He also asks: Is it permissible for a daughter to uncover the hijab or sit with her cousin (son of her father’s brother) or her cousin (son of her mother’s brother)?
The Shaykh: Before that, as for thin clothes that do not cover the awrah (nakedness), she should not wear thin clothes that reveal her thighs or reveal her awrah, or tight clothes. This is not permissible for her, even in the presence of her mahrams. It is not permissible. That is, she should wear covering clothes. The shilbah alone is also not something she should do in the presence of her mahrams, because the shilbah reveals much of her body, so she should not do that. But she should wear covering clothes and reveal her face and hands; there is no harm with her mahrams. Yes.
The presenter: May Allah reward you.