The husband's brother, his sons, and his sisters' sons are not mahram

Question:
My husband's sister's son has been with us in the same house since he was one year old, and now he is thirteen years old. Is it permissible for us to uncover him now that he has reached puberty? This is the first part of the question.

Answer:
It is not permissible; you may not uncover him, because he is a non-mahram. The husband's sister's son, the husband's brother's son, and the husband's brother himself are all not mahram; they are all non-mahram. Therefore, it is obligatory not to uncover them and not to be alone with any one of them, because they are not mahram. Yes.

The presenter: May Allah reward you with good. Are my sister's daughters permitted to uncover my husband when they reach puberty?

The Shaykh: Your sister's daughters are non-mahram to your husband, and likewise your own sisters are non-mahram; they are not permitted to uncover your husband. Yes. And they may not be alone with him; no one of them may be alone with him. Yes.

The presenter: May Allah reward you with good.