Can a girl of "Sadaat" (the family of Prophet, sallallaahu alayhi wa sallam, from Faatimah, may Allaah be pleased with her) marry a non-Sadaat man? Can a girl of Sadaat marry with a man from the non-Fatimid generation of Ali bin Abu-Talib, may Allaah be pleased with him?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

The criteria of suitability in marriage is judged based on one’s religion and good moral conduct. The Prophet said: “If a man whose religion and moral character are pleasing to you proposes to marry your daughter, then marry her off to him." [At-Tirmithi]  According to the most preponderant opinion the competence of family lineage is not considered as a condition in marriage. The Prophet married his slave Zayd Ibn Haaritha to Zaynab Bint Jahsh who is from the tribe of Quraysh, and married Usaamah Ibn Zayd to Faatimah Bint Qays who is also from the tribe of Quraysh; moreover, Bilaal Al-Habashi married the sister of 'Abdur-Rahmaan Ibn 'Awf who is also from the tribe of Quraysh of the family of Beni Zahrah and so forth.

Therefore, it is permissible for the people who are not from the same family lineage as that of the Prophet to marry a member of the family of the same lineage as that of the Prophet just like 'Umar, married Um Kalthoom Bint 'Ali all.

Allaah Knows best.