Now I shall answer the bold part of your dual question:
What is so special about the Family of the Prophet (s) ?
When the verse was revealed, the Muslims asked the Prophet: He replied,
alHakim alNaysaburi, alMustadrak `ala al-Sahihayn, volume 2, page 444
al-Qastallani, Irshad al-Sari Sharh Sahih al-Bukhari, volume 7, page 331
al-Suyuti, al-Durr al-Manthur, volume 6, pages 6-7
al-Alusi al-Baghdadi, Ruh al-Ma’ani, volume 25, pages 31-2
The position of truthfulness and virtue of the Ahl al-Bayt was further confirmed by the Qur’an during the disputation with the Christians of Najran. When the verse was revealed
, the Prophet (s) called ‘Ali, Fatima, al-Hasan and al-Husayn and said:
Muslim, al-Sahih, (English translation), book 031, number 5915
alHakim alNaysaburi, alMustadrak `ala al-Sahihayn, volume 3, page 150. He states that it is sahih in accordance with the criteria of al-Bukhari and Muslim
Ibn Hajar al-‘Asqalani, Fath al-Bari Sharh Sahih al-Bukhari, volume 7, page 60
al-Tirmidhi, al-Sahih, kitab al-manaqib, volume 5, page 596
Ahmad b. Hanbal, al-Musnad, volume 1, page 185
al-Suyuti, History of Khalifas Who Took The Right Way, (London, 1995), page 176
Isn’t it enough to show respect towards the Ahl al-Bayt ?
Is it sufficient to just show respect towards the Qur’an? Surely the Muslims have no choice but to follow it, as a source of Divine guidance, in all their affairs. The Prophet Muhammad (s) left two things as legacy to the Muslims, and promised that they will never separate from each other until the Day of Judgement. **By twinning the Ahl al-Bayt with the Qur’an, the Prophet (s) was telling us to not only show respect towards them, but also to take explanations of Islamic doctrine, practices, hadith and tafsir from them.
**
alHakim alNaysaburi, alMustadrak `ala al-Sahihayn, volume 3, p. 151 and volume 2, page 343.
He states that it is sahih in accordance with the criteria of Muslim
al-Suyuti, al-Durr al-Manthur, volume 1, pages 71-72
Ibn Hajar al-Makki, al-Sawa’iq al-Muhriqa, page 140. He states that this tradition has come down through many chains of narration that strengthen each other.
**Who are included in the Ahlul Bait?
**
It has been shown that the Family of the Prophet (s) – interchangeably referred to as the Ahl al-Bayt, ‘Itrah and Aal - included his daughter Fatima al-Zahra’, her husband Imam ‘Ali, and their children Imams al-Hasan and al-Husayn (‘a).
The members of this Family of five, with the Prophet Muhammad (s) at its head, were the ones alive at the time the Qur’anic verses regarding their virtue were being revealed to the Prophet (s). However, nine other Imams from the descendants of Imam al-Husayn (‘a) are also in this chosen Family, the final one being Imam al-Mahdi (‘a).
The Prophet (s) said:
al-Juwayni, Fara’id al-Simtayn, (Beirut, 1978), page 160. Note that al-Juwayni’s greatness as a scholar of hadith has been attested by al-Dhahabi in Tadhkirat al-Huffaz, volume 4, page 298, and also by Ibn Hajar al-‘Asqalani in al-Durar al-Kaminah, volume 1, page 67
[al-Juwayni, Fara’id al-Simtayn, page 160]
[Ibn Majah, al-Sunan, volume 2, page 519, numbers 4085-6; Abu Dawud, al-Sunan, volume 2, page 207]