incestuous

adjective2

1. •
   Pertaining to or engaging in incest.

   • If you engaged in an incestuous relationship with a family member, that would make you an inbreeder.
2. •
   (disapproving) Characterized by mutual relationships that are intimate and exclusive to the detriment of outsiders.

   • Democrats have the luxury of controlling the public narrative, thanks, in large part, to their incestuous relationship with the news media. — 2019