It is more common than you think for cousins to experiment, especially children with the age 9 to 13 years old. What really happens is that at that age young people have enormous sexual desires and they still don't know how to handle what they feel, they simply let themselves be dominated by their desires and things happen. The idea of two cousins having sex is generally considered disgusting. Cousins are relatives. You don't sleep with members of your own family. However, cousin relationships are "a deeply ingrained custom" among a fifth of the world's population, especially in Muslim communities in Southeast Asia and the Middle East, where blood relationships constitute 30-50 percent of the total. In the West, this practice is not as widespread, although in Europe and the United States this type of union was common until the middle of the 19th century, when consanguinity relations began to be condemned due to the rejection of the medical community.