Wikipedia:
Cousin relationships
See also: Cousin marriage and List of coupled cousins
Marriages and sexual relationships between cousins are viewed differently in many cultures and may or may not be seen as incest. In many countries, marriage between cousins is legal, whereas some follow a more restrictive doctrine and prohibit such marriages as incestuous, depending on the degree of the relationship.[45] Consanguineous unions remain preferential in North Africa, the Middle East and some parts of Asia, with marriage between first cousins being particularly common.[46] Communities such as the Dhond and the Bhittani of Pakistan clearly prefer marriages between cousins as they ensure purity of the descent line, provide intimate knowledge of the spouses, and ensure that patrimony will not pass into the hands of "outsiders".[47] Some cultures prohibit farther relations than first cousins from marrying and may extend these prohibitions to genetically unrelated individuals, as for example was the case in South Korea before 1997 when anyone with the same last name and clan was prohibited from marriage. In light of this law being held unconstitutional, South Korea now only prohibits up to third cousins (see Article 809 of the Korean Civil Code).
Obviously parents & siblings = incest but cousin is different from person to person.
Off to call my couz
