Near Relation Romance Theme
Tagged under Tropes.
This tag covers romantic relations between closely related characters e.g. mother/son, father/daughter, siblings. Yes,
step-siblings count.
"Selfcest" refers to romantic relations between a character and their
clone/alternate persona i.e. a separate version of themselves. In this case, the Dual Persona tag should also be used, along with either Shounen-ai or Shoujo-ai, if the alternate persona's
gender is the same as the original character's.
Only use this tag if the related characters interact
romantically with each other. This and this, for example, aren't cases of NRR but Love Triangles.
Also see: Androgyny, Gender Bender.