As-Salaam alaikum,
In his magnum opus, Meccan Revelations (al-Futuhat al-Makkiyya), Sayyadi Ibn Arabi (d. 1240), may Allah be Merciful to him, asserts that true lineage (al-nasab haqiqi) is not necessarily physical but results from one's relationship to Allah and from one's Divine knowledge (ilm). Hence the meaning of the famous tradition, "those who possess knowledge are the real heirs of the Prophets"- (al-ulama waratht al-anbiya): the mystics are the real heirs of the Prophets, because they have inherited the Prophetical heritage- God-given knowledge.

The Prophet's house (Sallallahu alaihi Wasallam) has 2 door-ways: the lower house.. his biological family and his higher house... Muhammad's spiritual family. In this regards, Ibn Arabi differentiates between the terms al and ahl: While ahl points to the biological family of the Prophet (as in the expression ahl al-bayt), al designates his closest and most unique companions (khassa)- the righteous ones, those who possess knowledge of Allah, the believers (al-salihuna al-ulama bi-llah al-mu'minuna)- the mystics, who enjoy general prophecy (nubuwa amma)... to be distinguished from legislative prophecy (nubuwa al-tashri). It may also happen, nevertheless, as in the case of Hassan, Hussein, Jafar al-Sadiq and others that certain members of ahl-bayt are also the al of Muhammad, ie righteous believers who possess Divine Knowledge.