They say there is no biological reason to discourage cousins from marrying. First cousins are somewhat more likely than unrelated parents to have a child with a serious birth defect, mental retardation or genetic disease, but their increased risk is nowhere near as large as most people think, the scientists said.

Do children of first cousins have birth defects?

The vast majority of children of first cousins are healthy and do not have problems due to their parents relatedness. It is important to keep in mind that even for an unrelated couple, there is an approximately 2-3% chance that their child is born with a birth defect, genetic syndrome, or disability.

Are first cousins inbred?

First cousins have an inbreeding coefficient of 0.0625. But the estimate that 0.2 percent of U.S. marriages are between people who are second cousins or closer needs to be treated with plenty of caution.

What happens if you have a baby with your siblings?

The risk for passing down a genetic disease is much higher for siblings than first cousins. To be more specific, two siblings who have kids together have a higher chance of passing on a recessive disease to their kids.

Is it legal for cousins to marry?

In the United States, second cousins are legally allowed to marry in every state. However, marriage between first cousins is legal in only about half of the American states. All in all, marrying your cousin or half-sibling will largely depend on the laws where you live and personal and/or cultural beliefs.