Who is Part of Ahlul Bayt? (For Shi'as)

"Ahl" is a accusative masculine noun. In Arabic, it covers several meanings. It begins with Husband and wife. And if they have children, they become part of the "Ahl." "Bayt" is genitive masculine noun and in Arabic it means lodging, household, family, or a place of dwelling. In the Quran Surah Hud 11:73, the Angels called Abraham and his wife "Ahlul Bayt." In Surah al-Ahzab 33:33 Allah says the same. So, there's no doubt, according to the Quran and the Arabic language; the husband, his wives, and his children are "Ahlul Bayt." However, I was surprised to read that both Shi'as and Sunnis extend the label "Ahlul Bayt" to others also. **Who do Shi'as consider to be from Ahlul Bayt and why?** If posting any hadith, please provide why do you consider the hadith authentic. Thanks.