Does what a person pays monthly to his deceased sister's son count as house rent from his obligatory Zakat, knowing that the nephew works for a salary that is not sufficient for him?

It is permissible to give the obligatory Zakat to a needy nephew (sister's son) with the intention of it being the prescribed Zakat. One should hand it over to him for him to spend as he wishes, because it is both a charity and an act of kinship, and because relatives have the primary right to kindness.