Bonded system

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Bonded systems are systems who are, in some way, bonded or attached to each other and feel uncomfortable using partner system due to its romantic connotations. The term was intended to be used in a platonic (e.g. best friend, familial) manner, but it can be used for any type of non-romantic relationship.

Related Terms
Partner system is another, more romantic, word to describe the relationship between two systems. A plush system is the queerplatonic variant of partner system. A sibling system is another familial term, but focused on a sibling-like relationship. A squish system is a platonic partner system.