in a way that involves sexual activity between people who are closely related and not legally allowed to marry

It was claimed that he was incestuously attracted to his sister. 据说他对自己的妹妹怀有不伦之恋。

The population of the village is almost incestuously interrelated. 村里人人都有血缘关系，几乎到了乱伦的地步。

in a way that involves only a close or limited group of people, who do not communicate or do business with people outside the group

The problem is that manufacturers are all incestuously linked these days. 问题是，这些年来，制造商都只搞小团体连带关系。

Members of both parties incestuously engaged in doling out political favours to their campaign contributors. 两党成员都搞小团体连带关系，向他们的竞选捐款人提供政治恩惠。