Janusmate

Not to be confused with janusian, a role regarding protector and persecutor qualities. undefined:

Janusmates or janmates are headmates that together embody duality in some way. Any two headmates that may be regarded as "two halves of a whole" may also be called janusmates (to each other).

Related Terms
Dualbased or gemini systems are similarly based in duality.

Dual conceptives, metamates, or systwins may present as janusmates.