Many cultures encourage first cousin marriages and their kids seem to be pretty safe. Recent studies have shown that the risk for first cousins to pass on diseases is only 2-3% higher than for unrelated people. But there is definitely good biology behind the laws that prohibit brothers and sisters from having children.

Can siblings get pregnant?

Many cases of incest can be recognized when pregnancy occurs. In the present case, an incestuous relationship between a male and female sibling younger than 15 years resulting in pregnancy has been examined.

Do Muslims marry their cousins?

Cousin marriage, or consanguinity (marriages among couples who are related as second cousins or closer), is allowed and often encouraged throughout the Middle East, and in other Muslim countries worldwide such as Pakistan.