Definition of "headmate"

The first one of the headmates (our word for alter) I was aware of was a boy named Josh.

2018, "The Entropy System", Toi Magazine, December 2018/January 2019, page 56

With co-fronting, typically only one headmate at a time functions as the ‘main fronter’ who does the majority of physical driving of the body, […]

2020, Tynan Drake, "Intersectional Representation: LGBTQ+ and neurodiverse voices in transmedia fiction", paper submitted to Ball State University, page 36

Each headmate has their own experiences, memories, emotions and requirements, thus should be spoken to and referred to in their own preferred way.

2021, Zarah Eve, Sarah Parry, “Exploring the experiences of young people with multiplicity”, in Youth and Policy