The exact date of the birth of Umar is not known. The concensus of opinion, however, is that Umar was born at Mecca around 580 A.D He was younger than the Holy Prophet of Islam by about ten years.
Umar belonged to the Adi clan of the Quraish. It was one of the ten clans of the Quraish who inhabited Mecca.
The pedigree of Umar was: Umar the son of Khattab; the son of Nufail; the son of Abul Uzza; the son of Riza; the son of Ribah; the son of Qurat; the son of Adi; the son of Katb.
The pedigree of the Holy Prophet was: Muhammad (peace be on him) the son of Abdullah; the son of Abdul Muttalib; the son of Hashim; the son of Abd Munaf; the son of Qussay; the son of Kulab; the son of Ka'b.
In the case of Abu Bakr and the Holy Prophet, Murrah in the eighth degree was their common ancestor. In the case of the Holy Prophet and Umar, Ka'b in the ninth degree was their common ancestor.
Among Umar's ancestors, Adi rose to prominence as a diplomat, and the clan came to be known after him. Whenever the Quraish of the day had to negotiate any settlement with any other tribe, Adi represented the interests of the Quraish as an ambassador. Even in the case of disputes among the Quraish themselves, Adi acted as the arbitrator. After the death of Adi the two offices of diplomatic representation and arbitration became hereditary in his descendants.
Umar's grandfather Nufail arbitrated in a dispute between Abdul Muttalib, the grandfather of the Holy Prophet and Harab bin Umayyah over the custodianship of the Ka'bah. Nufail gave his verdict in favour of Abdul Muttalib. Addressing Harab bin Umayyah he said:
"Why do you pick a quarrel with a person who is taller than you in stature; more imposing than you in appearance; more refined than you in intellect; whose progeny outnumbers yours and whose generosity outshines yours in lustre? Do not, however, construe this into any disparagement of your good qualities which I highly appreciate. You are as gentle as a lamb, you are renowned throughout Arabia for the stentorian tones of your voice, and you are an asset to your tribe."
This address is indicative of Nufail's skill in diplomacy and his highly developed sense of judgment.
Khattab the father of Umar was among the prominent members of the Banu Adis. The Banu Adis had some feuds with Banu Abdul Shams. The Banu Abdul Shams were stronger in power and position, and the Banu Adis as a safety measure had to seek alliance with some other clan. They allied themselves with Ranu Shams. On this alliance, Khattab composed the following verses:
"How can Abdul Shams still threaten us,
When other men of mettle espouse our cause?
In the halls of Banu Shams there are mighty warriors,
Whose hospitality and protection we enjoy."
The house in which Umar was born in Mecca was situated midway between Safa and Marwah. During the period of his caliphate, Umar had the house dismantled, and the site was turned into a camping ground.
Umar's mother was Khantamah who was the daughter of Hisham bin al-Mughirah. Al-Mughirah was a personage of high rank among the Quraish. In the event of war he marshalled the Quraish troops and led them to war. Hisham the maternal grandfather of Umar and al-Walid the father of the renowned General Khalid were brothers. Khalid was thus a cousin of Umar s mother and his maternal uncle.
Abu Jahl whose personal name was Amr bin Hisham bir al-Mughirah was a brother of Umar's mother, and his maternal uncle. One of the sisters of Umar's mother, Umm Salma was married to the Holy Prophet of Islam.
Umar had several brothers and sisters. The most well known out of these were: Zaid and Fatima. Zaid and Umar were step brothers, their mothers being different. Nevertheless the two brothers were devoted to each other. When Zaid was later martyred at the battle of Yamama during the caliphate of Abu Bakr, Umar was highly grieved. He used to say, "Whenever the wind blows from Yamama, it brings me the fragrance of Zaid."
Fatima was the real sister of Umar. She was married to her cousin Saeed bin Zaid bin Amr. She played an important role in the conversion of Umar to Islam.
Amr, a brother of Khattab was a paternal uncle of Umar. Zaid the son of Amr, and a cousin of Umar was among the distinguished persons of the Quraish, who before the advent of Islam gave up idolatry, and came to believe in the unity of God. Zaid was a poet. One of his poems reads:
"I believe in one God,
I cannot believe in a thousand gods.
I ignore the idols of Lat and Uzza,
A wise and cautious man can do no more."
Khattab the father of Umar persecuted Zaid for his religious beliefs. Zaid died before the Holy Prophet of Islam announced his prophetic mission. When the Holy Prophet proclaimed his prophethood, Saeed the son of Zaid who had married Umar's sister Fatima, was among the early converts to Islam.