From Pluralpedia, the collaborative plurality dictionary
soulbonder (adj.)
Applies tosystems, headmates

Soulbonders are hosts who feel an intense connection to a character to where that character becomes a headmate or takes a voice in their head, called a soulbond. These can be considered systems.

This differs from a kintype in that a soulbond is a separate person. However, a soulbonder may still have kintypes.