Previvmate

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A previvmate is a system member who knew at least one other system member in a past life, and has ended up in the same body in this life.

A previvmate may have been there from birth, or may have joined later, and may or may not have shared a body in their previous life as well.

The suffix -mate can also be replaced with -tive or -genic to fit the system/system member better.