Dear Br. M. As-salaamu alaykum. If you have physical evidence through a credible genealogist that your ancestors go back to the Ahl al-Bayt, then you may not take Zakat but you can drink water from the mosque. However, to our knowledge, this is a very rare case because most people claim to be related to the Ahl al-Bayt but they are not in reality. Thank you for asking and God knows best.
(Source: IslamiCity) Classified in Ahl al-Bayt >