monoprogeny
n.— «Three of my closest friends are also only children and, now in our mid-30s, we have been supporting and feuding with each other in a proto-sibling way since meeting at university. We realised this a few years ago, when a boyfriend commented on the tendency of monoprogeny—his disapproving coinage—to huddle together.» —“Plays well with others?” by Miranda Green Financial Times (United Kingdom) May 4, 2007. (source: Double-Tongued Dictionary)
Further reading
Patrick in New York City is curious about the term ride or die, which describes a friend, fan, or romantic partner who is devoted to the end. The expression shows up in the mid-1990s in hip hop and the work of Tupac Shakur and The Lox, and often...
Understanding the varieties of conversational styles can mean the difference between feeling you’re understood and being insulted. “High-involvement” speakers interrupt or talk along with someone else to signal their enthusiasm...