"If you asked any one of them, they wouldn’t know how to give you a good answer – or any answer really. They genuinely have no idea; they can’t pinpoint the moment they all came together and became that. It just… happened. There were probably some triggers; some of them started off as couples, or maybe even as triads, but it’s hard to tell now. It’s difficult to remember who was with who first; it’s tricky because they’re just them now."
Or, the one in which they all come together and love each other, and 'pack' means more than you could ever imagine [POLYAMORY].