incestuous

/ɪnˈsɛstʃuəs/
adjective
  1. Involving sexual relations between people who are too closely related to marry, such as parents and children or siblings.
    • The ancient royal families often had incestuous marriages to keep power within the dynasty.
    • In many cultures, incestuous unions are forbidden by law and social custom.
    • The novel explores the tragic consequences of an incestuous relationship between a brother and sister.
  2. Describing a group or organization that is too closed or self-involved, with members only interacting with each other and not with outsiders.
    • Critics say the company's incestuous hiring practices keep out fresh talent and new ideas.
    • The small theater community became incestuous, with the same actors directing and starring in each other's plays.
    • The political party's incestuous network of insiders made it hard for newcomers to gain influence.