There is a friendly/familiar or reciprocal relationship between A and B, and B has sex with a third party C. A does not consent to it or is unaware of the activity.Notes: A reciprocal relationship does not require reciprocal romance. Examples are childhood friends, personal friends, classmates, or work colleagues.Requires story elements showing the relationship between A and B, where they either are in a romantic partnership, or A has a romantic interest for B. B being taken away from A must be a notable part of the story.If the relationship between A and B is established in canon rather than as part of the story, then A must appear or be (directly or indirectly) referenced in the work in a relevant way for the tag to be applicable.Does not apply if all parties (A, B and C) are shown to be happy and satisfied with the resulting polyamorous relationships, except if the focus for the majority of the work is on A having B taken from them.