Allah says: “O Prophet! We have made lawful to thee the wives to whom thou hast paid their dowers; and those whom thy right hand possesses out of the captives of war whom Allah has assigned to thee; and daughters of thy paternal uncles and aunts, and daughters of thy maternal uncles and aunts, who migrated with thee; …”
Allah has made marriage with first cousins lawful. There is no dispute about this in Islamic Law. Anyone who wishes to dispute with this is placing his own religion in serious danger.
What the questioner mentioned that he does not like to marry his cousin, because he feels she is like his sister, is something based on the customs and traditions of certain societies. However, these customs cannot make it forbidden for a man to marry a woman. It is well established in Islamic Law that this kind of marriage is good and acceptable. In fact, many families prefer marriages between cousins.
Zaynab was the first cousin of the Prophet (peace be upon him). Her mother was Umaymah, the daughter of his grandfather `Abd al-Muttalib. We can find no better example than that of the Prophet (peace be upon him), since he is the one Allah has ordered us to follow. If no one else in history ever married his cousin, the precedent of our beloved Prophet (peace be upon him) would be more than sufficient for us.
We are surprised that someone would make such a claim that none of the Companions ever married his first cousin. There were no marriage records back then at all, and frankly, marrying one’s cousin was not considered a big deal. It was quite commonplace and not worthy of special notice or special mention. It is not surprising; therefore, that someone will have a hard time to find a record of its occurrence.
Nevertheless, a cursory investigation of the hadîth literature quickly turned up a couple of examples. The illustrious Companion al-Mughîrah b. Shu`bah married the daughter of his uncle, the illustrious Companion `Urwab b. Zubayr al-Thaqafî. [As related by Sa`îd b. Mansûr in his Sunan]
Kabshah bint Ka`b was married to the son of her uncle, the famous Companion Abû Qatâdah. In the well-known hadîth about the cat not being impure, Abû Qatâdah refers to his daughter-in-law as his niece (literally: “daughter of my brother”). A woman named Kabshah bint Ka`b once poured out some water for her father-in-law Abû Qatâdah to use for his ablutions. A cat came along wanting to drink, so Abû Qatâdah turned the bowl so the cat could do so. He noticed Kabshah looking at him strangely and said: “Does this surprise you, my niece? Indeed Allah’s Messenger said regarding the cat: “It is not impure. It is one of those creatures that live in our attendance.”
Also, it is well known that `Alî b. Abî Tâlib, the fourth Caliph and dearest Companion of the Prophet (peace be upon him), gave his daughter Zaynab in marriage to her first cousin `Abd Allah, the son of his brother Ja`far b. Abî Tâlib. This is the act of one of the Rightly Guided Caliphs (al-Khulafâ’ al-Râshidûn).
The Prophet (peace be upon him) said: “You must follow my Sunnah and the Sunnah of the Rightly Guided Caliphs who come after me. Hold fast to it with your molar teeth.”
We hope that you can see that there is no basis for disputing the issue of a Muslim marrying his first cousin. It is established by the Qur’ân, the Sunnah, the practice of the Companions including the Rightly Guided Caliphs, and the consensus of the Muslim Ummah.