From Pluralpedia, the collaborative plurality dictionary

A sysparent is a headmate that is considered to be a parent of another headmate.

sysparent (n.)
Applies toheadmates

This includes a headmate that comes from either one's own system, or someone else's. It could be adopted, or by blood

In general, it refers to parental figures plural-wise. One compare it to a parental figure in non-plural situations.