List of coupled siblings

There are many terms used to describe a romantic bond between siblings, including nomenclature like adelphogamy, the more general syntax associated with formality like consanguinamory, specific hyponyms such twincest, or slang terms like sibcest.[1][2] In mostly a heterosexual context, a female partner in such a relationship may be referred as a sister-wife.[3] A similar incestual arrangement which is non-monogamous can be referred as sister-swapping or brother-swapping[4], although this should not be confused with berdel which describes a parallel situation wherein families exchange multiple brides or bridegrooms.[5]

While cousin marriage is legal in most countries, and avunculate marriage is legal in many, sexual relations between siblings are considered incestuous almost universally. Sibling incest is legally prohibited in most countries worldwide. It was historically practiced in Ancient Egypt and Rome, and indigenous Inca tribes.

Innate sexual aversion between siblings forms due to close association in childhood, in what is known as the Westermarck effect. Children who grow up together do not normally develop sexual attraction, even if they are unrelated, and conversely, siblings who were separated at a young age may develop sexual attraction. Thus, many cases of sibling incest, including accidental incest, concern siblings who were separated at birth or at a very young age.

• Avunculate marriage
• Consanguinity
• Cousin marriage