The pure and blessed Prophet salla Llahu ‘alayhi wa sallam married the pure daughter of Sayyidina ‘Umar radiya Llahu ‘anhu, Sayyidah Hafsah radiya Llahu ‘anha.
The grandson of the fourth Imam married the daughter of Khalid ibn Abi Bakr ibn ‘Abdullah ibn ‘Umar ibn al Khattab.
Ibn ‘Inabah writes:
As for Hussain ibn al Aftas, whose mother—according to Abu al Hassan al ‘Umari—was from the progeny of ‘Umar, the daughter of Khalid ibn Abi Bakr ibn ‘Abdullah ibn ‘Umar ibn al Khattab.
Mus’ab al Zubairi says:
… His mother was Juwairiyah bint Khalid ibn Abi Bakr ibn ‘Abdullah ibn ‘Umar ibn al Khattab.
The son of Sayyidina Hassan radiya Llahu ‘anhu, grandson of Amir al Mu’minin ‘Ali ibn Abi Talib radiya Llahu ‘anhu, married Ramlah bint Sa’id ibn Zaid ibn ‘Amr ibn Nufayl. They were blessed with three children from this union: Muhammad, Ruqayyah, and Fatimah.
Ibn ‘Inabah mentions:
Hassan al Muthanna had another son, whose name was Muhammad, and two daughters: Ruqayyah and Fatimah. Their mother was Ramlah bint Sa’id ibn Zaid ibn ‘Amr ibn Nufayl al ‘Adawi. The progeny of Muhammad ibn Hassan al Muthanna did not continue.
The blessed granddaughter of the Rasul salla Llahu ‘alayhi wa sallam, the daughter of ‘Ali and Fatimah radiya Llahu ‘anhuma, was married to Sayyidina ‘Umar ibn al Khattab radiya Llahu ‘anhu.
This marriage took place without any doubt, even though the sceptics may deny it. It is proven in the major sources of history and genealogy. Anyone who peruses the book Al Asili of Ibn Tiqtaqa (pg. 58) with the annotations of Mahdi al Raja’i will see the reality of this marriage.
Ibn Tiqtaqa writes while discussing the daughters of Amir al Mu’min ‘Ali ibn Abi Talib radiya Llahu ‘anhu:
And Umm Kulthum, whose mother was Fatimah al Zahra’ ‘alayh al Salam, married ‘Umar ibn al Khattab. They had a son named Zaid. Thereafter (after ‘Umar’s demise) she married ‘Abdullah ibn Jafar.
Zaid ibn ‘Umar used to say:
I am the son of two Khalifahs.
Referring to his father, ‘Umar, and his grandfather, ‘Ali ibn Abi Talib radiya Llahu ‘anhuma.
The researcher of the book added a lengthy footnote establishing this marriage, citing the great genealogist Abu al Hassan al ‘Umari:
It is recorded in al Majdi (pg. 107): Umm Kulthum bint ‘Ali—daughter of Fatimah, whose name was Ruqayyah—was wed to ‘Umar ibn al Khattab. She bore him a son named Zaid. Both Mother and son passed away on the same day.
The honourable ascetic, the historian of Baghdad Abu Muhammad al Hassan ibn al Qasim ibn Muhammad al ‘Uwayd al ‘Alawi al Muhammadi rahimahu Llah has reported that the person who ‘Umar married was a female Jinn, others from our school presume that he did not consummate the marriage, and yet others say, “She was the first to be forcibly taken in Islam.” [However,] more reliable than these narrations [presumptions] is what we have just seen that ‘Abbas ibn ‘Abdul Muttalib married her to ‘Umar with the consent of her father ‘alayh al Salam. She then bore for ‘Umar a son named Zaid.
I say: Most certainly Mahdi al Raja’i quoted the statements of al Murtada which suggest that this was coerced but Mahdi al Raja’i also mentioned thereafter, “There is a lengthy discourse in refutation and negation of this, which need not be mentioned at this juncture.” He thus attempted to abridge the discussion, but we will shed more light on the issue.
The problem with this [Shia] rationale is as mentioned by al Musawi in his book, al Sayyidah Sukaynah bint Hussain Bayna Haqa’iq al Tarikh wa Awham al Mu’arrikhin. He mentions that it has been reported that she (Sukaynah radiya Llahu ‘anha) was forcefully married to Mus’ab al Zubairi. This is absurd and will not be believed by anybody [of sound disposition] as it is such a vilification of the entire clan of Banu Hashim which no sane person will believe. The Banu Hashim are the most honourable of clans—this is known to all and sundry—and at that period in time they possessed both power and numbers; no person would dream of besmearing them due to their unparalleled courage and unsurpassed camaraderie towards their own. An ordinary Bedouin Arab—having no special lineage, position, knowledge, or piety—would lay down his life to defend those he loves if anyone intended to harm them. When an ordinary Bedouin Arab will fight those who seek to harm his loved ones, whether the act be justified or not, then what should we think of the Banu Hashim—the Ahlul Bayt of the Prophet salla Llahu ‘alayhi wa sallam? The following incident is recorded in a number of sources, but I will suffice with what Ibn ‘Inabah has mentioned in ‘Umdat al Talib (pg. 90, Ansariyan) when discussing Hassan al Muthanna:
His agnomen was Abu Muhammad, and his mother was Khawlah bint Manzur ibn Zaban ibn Sayyar ibn ‘Amr ibn Jabir ibn ‘Aqil ibn Sumay ibn Mazin ibn Fazarah ibn Dhibyan. She was first married to Muhammad ibn Talhah ibn ‘Ubaidullah, who was martyred during the battle of Jamal (thus leaving her a widow). She had children from this marriage as well. She was then married by Hassan ibn ‘Ali ibn Abi Talib ‘alayh al Salam. When her father, Manzur ibn Zaban, heard of this he came to Madinah, and grounded his flag at the entrance of the Masjid. Not a single person from the Banu Qais was left except that he had gathered under the flag, he (Manzur) then said, “Will the likes of me have matters decided about his daughter without his consent?” The crowd replied, “Never!” When Hassan saw this, he returned his daughter. She was then placed in her carriage and taken out of Madinah.
When they were passing Baqi’, she said to her father, “O my father, where are you going? He is Hassan ibn Amir al Mu’minin ‘Ali and the son of the Prophet’s daughter radiya Llahu ‘anha.”
He replied, “If he desires you, he will come after us.”
As they were passing through the date orchards of Madinah, they were intercepted by Hassan, Hussain, and ‘Abdullah bin Jafar; so he handed her over to them and they returned with her to Madinah.
This incident conveys a deep message, ponder over it carefully respected reader!
The great granddaughter of Amir al Mu’minin ‘Ali ibn Abi Talib radiya Llahu ‘anhu was married to the great grandson of ‘Abdullah ibn ‘Umar radiya Llahu ‘anhu, Abu Bakr (ibn Qallamas) ibn ‘Uthman ibn ‘Ubaidullah ibn ‘Abdullah ibn ‘Umar ibn al Khattab.
 ‘Umdat al Talib, pg. 315, Ansariyan.
 Nasab Quraysh, pg. 73.
 Al Asili, pg. 58.
 Al Wafi bi al Wafayat, vol. 1 under the biography of Zaid ibn ‘Umar; Tarikh Islam, 1/502.
 Most noteworthy is that the ancestry of this famed genealogist, who is considered a reference for all those who came after him—often quoted by Ibn ‘Inabah in ‘Umdat al Talib and Ibn al Tiqtaqa in Al Asili, and many others—links to ‘Umar al ‘Atraf, which why he is called al ‘Umari. Mahdi al Raja’i said in his biography of him, “He is Abu al Hassan al ‘Umari, an esteemed Sayyid, renowned genealogist, author, and researcher. He wrote extensively on the ancestry of the progeny Abu Talib (Talibiyin), in a comprehensive work numbering many volumes. He also wrote Al Majdi for the governor of Egypt. He was born in Basrah 348 A.H and passed away in Mosul 460 A.H. Al Asili, footnotes, pg. 45. I say: He recited to Sheikh al Sharaf al ‘Ubaidali (d. 435 A.H) and to Ibn Tabataba Abu ‘Abdullah Hussain ibn Muhammad ibn Abi Talib ibn Qasim ibn Abi al Hassan Muhammad ibn Qasim ibn ‘Ali ibn Hassan ibn Ibrahim ibn Tabataba, the genealogist and his scribe.
 Al Asili, pg. 58, 59, footnotes.
 Qallamas refers to an esteemed noble and one who is extremely meritorious.