Consanguinity is usually defined as the result of a sexual reproduction between two related individuals. It can also refer to populations sharing at least one common ancestor, as those who live within isolates or within communities practicing endogamy. Second or higher order related couples and their offspring represent more than 10% of the current world population. The highest levels of consanguinity are found in the Southern and Eastern shores of the Mediterranean Basin, and the most concerned region extends from the southern shore of the Mediterranean Sea to Southeast Asia through Middle-East, Gulf and India. In Maghreb countries, consanguineous marriages are wide-spread. The rates for this practice vary from 23% in Morocco to 60% in Tunisia, with highest rates being found in rural areas. In Algeria, consanguineous marriages represent more than 38% of all marriages. Large scale migrations from South countries to North countries in the second half of the twentieth century had legal impact on migrants for these specific unions. As a consequence, controversies have been rising in the United States and the United Kingdom especially when a fast decrease of inter-related individuals unions seems unlikely. Consanguinity certainly increases the risk of autosomal recessive pathology, but what about mental pathologies with complex and polygenic heredity? The necessity of an awareness of the genetic risks of consanguinity is as essential in countries where inter-cousin unions are culturally encouraged as among migrant populations in Europe.