Cousin marriage in Islam:
allowed, and worth a test.

What the Quran says

Surah An-Nisa, verse 23, lists the women a man may not marry: his mother, daughter, sister, father's sisters, mother's sisters, brother's daughters, sister's daughters, foster mother and foster sisters, mother-in-law, stepdaughters (in certain cases), daughters-in-law, and two sisters at the same time. The next verse says that others beyond these are lawful.

Cousins aren't on the list, so cousin marriage is permitted. Islamic tradition records that the Prophet Muhammad married Zaynab bint Jahsh, the daughter of his paternal aunt, and his daughter Fatima married Ali, his cousin.

Nieces are on the list, so uncle–niece marriage isn't permitted in Islam, even though it's a custom in some other communities.

How common it is

• Pakistan: in the 2017–18 national survey, about 63% of married women had married a blood relative, and about half had married a first cousin.
• India: about 11% of all marriages are between relatives (NFHS-5), higher in some communities and regions.
• Saudi Arabia: about 56% of mothers in a 2004–05 national study were married to a relative.
• UK: in Bradford, 37% of babies of Pakistani heritage born in 2007–11 had first-cousin parents. That share has since fallen.

Families choose cousin marriage for good reasons: the families already know and trust each other, a daughter stays close to home, and family ties stay strong.

What the genetic risk really is

Everyone carries a few silent gene variants. A child is affected by a recessive condition only if they inherit the same variant from both parents. Cousins share grandparents, so they're more likely to carry the same variant.

• For first cousins, the chance of a serious birth defect roughly doubles, from about 3% to about 6%.
• In the Born in Bradford study, marriage between relatives accounted for about 31% of birth anomalies among babies of Pakistani heritage.
• Where cousin marriage repeats over generations, risk builds up, and couples who think of themselves as distant relatives can face first-cousin-level risk.

The risk is real and worth acting on, and most children of cousins are born healthy. The full numbers.

Is genetic testing accepted in Islam?

Widely, yes. Several Muslim-majority countries build it into marriage:

• Saudi Arabia has required premarital screening for sickle cell disease and thalassemia since 2004. Couples get their results, and marriage certificates are issued either way.
• Iran added thalassemia screening to its mandatory premarital tests in 1997, and affected births fell sharply.
• Pakistan has provincial laws on premarital thalassemia screening, and a national bill was reported passed by the National Assembly in 2026. Details here.

A test doesn't decide whether you marry. It gives you information. If a couple both carry the same condition, they can still marry and plan with a genetic counselor; options include testing during pregnancy and IVF with embryo testing, which many scholars permit for married couples using their own eggs and sperm. Ask a scholar you trust about the options that fit your beliefs.

What cousin couples can do

• Test for thalassemia and sickle cell with a Hb HPLC test, both of you.
• Consider an expanded carrier screen. Guidelines suggest it for couples who are second cousins or closer. In a study of high-risk couples in Pakistan, 45% received a result that could change their decisions.
• Not sure how closely you're related? If your families have married each other more than once, a DNA relatedness check measures how much you actually share.
• Share family history: any known conditions on either side are important.

We don't take religious positions. This page is health information so couples can decide for themselves.

Sources

1. The Quran, Surah An-Nisa 4:23–24 (Quran.com)
2. Dawn: Consanguineous marriages in Pakistan (citing PDHS 2017–18)
3. Consanguineous marriage in India, NFHS-5. Biodemography and Social Biology (2026)
4. El-Mouzan MI et al. Consanguinity in Saudi Arabia. Saudi Medical Journal (2007)
5. Sheridan E et al. Risk factors for congenital anomaly in a multiethnic birth cohort (Born in Bradford). The Lancet (2013)
6. Small N et al. Changes in consanguineous marriage in Born in Bradford cohorts. Wellcome Open Research (2024)
7. Bennett RL et al. Genetic counseling and screening of consanguineous couples and their offspring (NSGC). J Genet Couns (2002)
8. Memish ZA, Saeedi MY. Six-year outcome of the national premarital screening programme in Saudi Arabia. Annals of Saudi Medicine (2011)
9. Samavat A, Modell B. Iranian national thalassaemia screening programme. BMJ (2004)
10. National Assembly of Pakistan: premarital thalassaemia screening bill (2026)
11. Akbar et al. Expanded carrier screening in high-risk couples in Pakistan. Prenatal Diagnosis