When Imam Ali lost his wife, Fatima the daughter of Prophet Mohammad (peace be upon him and his household), he summoned his brother Aqil who was a well-known genealogist to ask him to search for a lady being the descendant of heroes so that she would give birth of a courageous, immaculate hero whose mission would be supporting his brother in the field of Karbala.1
Without hesitation, Aqil advised his brother to propose to Umm-ul-Banin; from the tribe of Kelab, because her fathers and people had been the foremost among others in fields of heroism and courage.
Agreeing to his advice, Imam Ali asked his brother, Aqil, to go to that lady's father and ask her hand for him.
As soon as Aqil mentioned the matter with him, Aamir -Umm-ul-Banin's father- welcomed and responded with pride.
Some historians2 have confirmed that Imam Ali married Umm-ul-Banin after the death of his first wife Fatima the Veracious (peace be upon her).
Others3 have recorded that Imam Ali had married Imama, daughter of Zaynab daughter of the Prophet, before Umm-ul-Banin.
* Adopted from the book : "Al-Abbas"