To be someone who has engaged in acts of incest

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.

A hill Billy term used for fucks under the age of 15 usually to talk about previous or upcoming sexual events of intercourse with direct family members

When two relatives have kids. For example, when Oedipus and his mom got down their kids were incested.