Incest between twins

Incest between twins or twincest is a subclass of sibling incest and includes both heterosexual and homosexual relationships. While in modern Western European culture such behaviour is considered taboo, incest between twins is a common feature in Indo-European, Asian (such as Japan, the Philippines, and Bali) and Oceanian mythology, and there are a few societies in which the prohibition on it is limited or it is partially accepted.