Yes, some people talk about tertiaries and so on. Triads - three people involved in some way. In a vee, the arm partners are not as commonly close to each other as each is to the pivot. Sometimes also called a triad. This is a different form of familial immortality than the traditional one of successive generations of children.
Geometry can get complicated, and creative nomenclature abounds.
As in every other aspect of polyamory, the precise bonds of intimacy vary from group to group and from member to member within groups. Others, including some long-term polyamorists, feel jealousy, which they regard as a signal that something needs investigation and care, much as they would regard depression or pain. Nobody has a trademark on How It's Done, if that's what you mean. We'll talk about everything. What they said.