Why is it not permissible to say "peace be upon them" to the Family of the Prophet (Ahl al-Bayt), and why is it not permissible to greet them with "peace," despite the existence of the verse "Peace be upon the family of Yasin" [Quran 37:130], and yet you say "may God's blessings and peace be upon him and his family"?

"Peace be upon the Household of the Prophet and the Companions, following the greeting of peace upon the Prophet, is prescribed. However, singling out the Household of the Prophet for blessings (salat) without including the rest of the Companions is disliked (makrooh), as it was not customary among the Companions and their successors (Tabi'een). As for some people’s argument using the verse from Surah As-Saffat to interpret it as referring to the Household of Muhammad, it is incorrect. The intended meaning there is the Prophet Elijah (Ilyas), as indicated by the context and the common recitation of the verse: 'Peace be upon Eliasins (Ilyas and his followers).'"