Re: What was the family relationship between Hazrat Umar and Hazrat ali ?
I wish that you had my post (quoted above) well and pondered over it.
-
I am surprised that narrations from your Infallible Imams have no value for you. I was certain that it would have sufficed - but alas

-
I have given you references from Sunni sources – not to convince you as understandably it would have no effect on you but just to reinforce references from Shia sources but alas

-
I have given you reference from well-known Shia Site Islam.org where Shia Scholar has very grudgingly accepted that fact that Hz. Umar (ra) had married Lady Umm Kulthum bint Ali (ra)! but alas

You asked for more from Sunni sources – So I think the following two would suffice.
I was informed by Anas ibn ‘Iyad al-Laythi, who reports on the authority of Jafar ibn Muhammad [as-Sadiq], and he from his father [Muhammad al-Baqir] that—Umar ibn al-Khattab asked Ali ibn Abi Talib for the hand of Umm Kulthoom in marriage. Ali said, “I had kept my daughters for the sons of Jafar.” Umar said, “Marry her to me, O Abul Hasan, for by Allah,there is no man on the face of the earth who seeks to achieve through her good companionship that which I seek to achieve.” Ali said, “I have done so.”
Then Umar came to the Muhajirun between the grave [of Rasool-Allah] and the pulpit. They—Ali, Uthman, Zubayr, Talhah and Abd ar-Rahman—used to sit there, and whenever a matter used to arrive from the frontiers, Umar used to come to them there and consult with them. He came to them and said, “Congratulate me.” They congratulated him, and asked, “With whom are we congratulating you, O Amir al-Mu’minin?” He replied, “With the daughter of Ali ibn Abi Talib.”
(source: Ibn Sa‘d in his work “at-Tabaqat al-Kubra”, vol.8, p.338, ed. Muhammad ‘Ab al-Qadir ‘Ata, “Dar al-Kutub al-‘Ilmiyyah”, Beirut 1990)
Biography Ibn Sa‘d
Ibn Sa’d was born in the year 168AH/784CE)[3] and died in 230AH/845CE.[3] He was a Sunni Muslim scholar of Islam and an Arabian biographer, received his training in the tradition from Al-Waqidi and other celebrated teachers. He lived for the most part in Baghdad, and had the reputation of being both trustworthy and accurate in his writings, which, in consequence, were much used by later writers.
Ibn Sa`d was from Basra, Iraq, [1] then lived in Baghdad in the 9th century. He is said to have died at the age of 62 in Baghdad. and was buried in the cemetery of the Syrian gate.
Ibn Qutayba said in al-Maarif (Beirut: Dar al-Kutub al-Ilmiyya, 1987) p. 122:
“THE DAUGHTERS OF ALI IBN ABI TALIB: As for Zaynab the elder the daughter of Fatima, she was [married] with Abd Allah ibn Jafar and gave him children whom we already named. As for Umm Kulthum the elder, also the daughter of Fatima, she was [married] with Umar ibn al-Khattab and gave him children we also already named. When Umar was killed Muhammad ibn Jafar ibn Abi Talib married her. He died before her then Awn ibn Jafar ibn Abi Talib married her and she died before him. The rest of Ali's daughters were married off to the sons of Aqil and the sons of al-Abbas except Umm al-Hasan -- she was married to Jada ibn Hubayra al-Makhzumi – and except Fatima – she was married to Sa`id ibn al-Aswad of Banu al-Harith ibn Asad.”
The same Ibn Qutayba also says in the same book (p. 107):
“THE CHILDREN OF UMAR IBN AL-KHATTAB FROM HIS BLOOD AND THEIR DESCENDENTS: .... also Fatima and Zayd, their mother being Umm Kulthum the daughter of Ali ibn Abi Talib from his union with Fatima the daughter of the Messenger of Allah upon him blessings and peace. It is also said that Umm Kulthum’s daughter from `Umar was named Ruqayya…”
Ibn Qutaybah (828 – 885 CE / 213 – 276 AH) was a renowned Islamic scholar of Persian origin.
I’m glad and have noticed that you are keeping this debate very civil and you must appreciate that
on my part I’m doing the same. I’m sure you must be aware that there are references in Shia literature regarding to this very topic (marriage of Hz. Umm Kulthum with Hz. Umar (may Allah be pleased with them both) which shows Imam using very inappropriate language. So let’s leave those bits out. Once again I appreciate your stance.
I feel that I have been dragged back into the ‘fray’ I have said enough and I don’t have luxury of time on hand.
Please I hope that now you won’t demand that I provide the Nikah document or the name of the witnesses to the marriage contract or how many camels were slaughtered to celebrate the momentous occasion. I won’t be able to. Let’s leave it to the viewers here to make up their own minds reading all the material provided by all the participants.
But where is originator of this thread???