The correlations of IQs of unrelated versus related persons reared apart or together suggest a genetic component to intelligence. For relationships where no genes are shared (such as adoptive parent-child pairs or similarly aged unrelated children raised together), the IQ correlation is around 21 to 32 percent. For relationships sharing 25 percent of genes (such as half-siblings), it is around 33 percent. Relationships sharing 50 percent of genes (such as parent-children pairs and fraternal twins raised together) have correlations roughly 44 and 62 percent, respectively. Identical twins, who share 100 percent of their genes, exhibit a nearly 80 percent IQ correlation even when raised apart.