Is the aunt a mahram (a relative one may not marry) to the husband of her sister's daughter?

The questioner:
May Allah reward you. She says: Is the husband of my sister's daughter a mahram to me? And is it permissible for me to appear before him while covering my hair?

The Shaykh:
Yes, he is not a mahram to her. The aunt is not a mahram to the husband of the sister's son. Yes.

The questioner:
She says: Is it permissible for me to appear before him while covering my hair and wearing covering clothes without tabarruj (a woman's display of her adornment)?

The Shaykh:
There is nothing wrong with her appearing before him while wearing the hijab as prescribed for the hijab, but she must not be alone with him.

The questioner:
She uncovers her face.

The Shaykh:
And I am wearing the hijab, we said.

The questioner:
I say, then covering my hair, then.

The Shaykh:
It is not sufficient; she must cover her face and her entire body from him because he is a non-mahram, and she must not be alone with him either.

The questioner:
And is it permissible for me to sit with his brother, or only with the husband of my sister's son?

The Shaykh:
All men who are not among her mahram (relatives one may not marry) require her to wear the hijab in front of them. There is no harm in her sitting with them, but without ikhtilat (free mixing of men and women), and without khalwah (seclusion with a non-mahram), and she must be wearing the hijab if she is safe from fitnah (trial, discord or temptation). Yes.