People who have gone through an unforgettable phase in life, and have some common experience to draw from in future conversations to keep them spiritually and emotionally bonded strongly.
Rarely found in the wild, and mostly formed while in captivity like in a conscript army for example.
Useless fact of the day: From telemarketing training for loans, there are secure and unsecure loans banks can offer to consumers. Secure loans are for things like cars and houses where upon default on payment, the bank can claim the property. Unsecured loans are like study loans for students and home renovation loans where the bank is unable to get back anything for sure if the borrower does not pay up. The joys upon discovering a flaw in the capitalist society: there IS something they can't own after all!