Does the wife's paternal uncle or maternal uncle fall under the concept of "al-hamu" (male in-law)? Is it permissible for a woman to be in seclusion with them in the house? And what should the husband do if he finds his wife's paternal uncle wearing his clothes after he had taken them off inside the house?

The paternal and maternal uncles of a woman are considered her mahram (unmarriageable kin), and it is permissible for them to be in khalwa (private seclusion) with her and to travel with her, unless there is fear of fitna (temptation/strife) from them, in which case khalwa is forbidden. As for the hamw (husband's male relatives), such as his brother, paternal uncle, and paternal cousin, they are not mahram, and the Messenger likened them to death. It is the husband's right that his wife not allow anyone he dislikes to tread on his bed, or to admit anyone into his house without his permission, even if they are her mahram. The husband, however, should not prevent anyone unless there is a known or suspected doubt. And beware of accusing a Muslim of indecency or slandering the wife's honor, as this could be a whisper from Satan.