Sunday Times 2
When cousins marry: Sri Lanka’s quiet genetic problem
View(s):Dr Ruben Thurairajah
A few years ago, Sri Lankan doctors collected marriage records from 22 districts. In just six months, they studied more than 5,000 weddings.
When the results came out, they were surprised. About 7 in every 100 couples were blood relatives—cousins or closer. Among Sinhalese and Muslims, the rate was small, around 4%. But among Tamils, it was almost one in four.
The same study looked at families that have children with thalassaemia, a serious inherited blood disease. Among those families, 15% of the parents were related by blood. For Tamil thalassaemia families, the number was close to 50%.
These figures show that while cousin marriage is not widespread nationally, it is deeply rooted in some communities, and it carries quiet risks.
Why cousin marriage continues
For many families, the reasons are practical, not stubbornness.
Money and land: Cousin marriages keep property “in the family”. When inheritance is shared among relatives, marrying inside the family circle helps prevent land disputes.
Trust and familiarity: In rural areas, families already know each other’s background. Parents feel safer choosing a partner from among their relatives.
Custom: In arranged marriages, the first search for a partner often begins with the extended family. Studies show arranged marriages are twice as likely to be between relatives compared with love marriages.
History and war: In the North and East, where decades of conflict reduced social networks and travel, families often turned to cousins because the pool of eligible partners was small.
The hidden cost
Doctors explain that when cousins marry, their children have a slightly higher chance of inheriting the same faulty gene from both parents.
Most children from cousin marriages are perfectly healthy. But when a rare disease already exists in a community, the risks grow over generations.
The clearest example is beta thalassaemia, a severe blood disorder. Children with this illness need regular blood transfusions for life and expensive medicine to prevent damage to the heart and liver. It costs the government millions of rupees each year and is a heavy burden for families.
Doctors also report higher chances of birth defects and developmental delays among some cousin-marrying families. These are not certainties—just increased risks that deserve attention, not stigma.
How to change course—gently
Many people ask if the government should ban cousin marriage. The experts say no. Bans rarely work and only create secrecy and resentment.
Instead, the answer lies in education and awareness.
1. Testing before marriage: Hospitals across Sri Lanka already offer quick tests to see if someone carries the thalassaemia gene. If both partners are carriers, doctors can give advice and options. Sadly, many couples are tested only after their first affected child is born.
2. Community education: Local voices matter most—teachers, midwives, priests, and respected elders. Simple explanations help: “If both parents carry the same gene, there’s a one-in-four chance that their child will be sick.”
3. Youth awareness: Adding basic genetics to school lessons would give young people the knowledge to make informed choices, just as they already learn about dengue and nutrition.
4. Gentle incentives: Instead of bans, small rewards—like reduced marriage-registration fees for couples who get tested—could encourage more people to take the test.
Supporting families
already affected
Sri Lanka now has more than 2,000 children living with thalassaemia. Their lives revolve around hospital visits and transfusions. These families need understanding, free treatment, and community support—not blame.
Showing compassion sends a clear message: every child matters, and no family should feel shame for a health problem they didn’t cause.
A humane middle path
Cousin marriage is not a national crisis. But neither is it harmless. For most, it seems a natural family choice; for a few, it brings lifelong hardship.
The way forward is simple: replace silence with information.
If young people know their carrier status and if families see examples of healthy, informed choices, the practice will naturally decline.
Sri Lanka has defeated diseases before—malaria and COVID-19. With the same mix of science and compassion, it can face this quiet genetic problem too.