Contrast with Parental Incest, where the parent/child power dynamics can make it even squickier. Not to be confused with Double In-Law Marriage, where both of the couples are Not Blood Siblings but siblings-in-law. NOTE: This trope is for actual cases of incest in-story. Incestuous subtext goes in Incest Subtext. Sibling incest is often thought to be the least harmful form. Although one of the key aspects of incest is the difference in power between the perpetrator and the victim, sexual behavior between two siblings of equal power, where touching, looking, and exploring are mutual decisions, can still pose problems for the participants and/or parents.