incestuous
adj. C1 Advanced US //ˌɪnˈsɛstʃwəs// UK //ɪnsˈɛstʃuːəs// in·ces·tu·ous
adj. describing a sexual relationship between people who are closely related by blood. It can also describe a situation where a small group of people only deal with each other, like a family business.
adj. relating to or involving sexual relations between close blood relatives. In a figurative sense, it describes a situation where a small group operates in isolation from the outside world, such as a family-run business or a closed social circle.
The family business is so incestuous that everyone is related.
The committee was criticized for being incestuous, as all the members were former colleagues from the same university department.
From incest + -ous.