im def not as eloquent n experienced as other commenters here but. input of a fresh face in a community matters too.
for me it was like. my plural partners kinda suspected i might be plural, similar to an egg yeah, n an inter-polycule joke started up abt that n jokingly lightheartedly trying to coax a headmate out of me. anyways my response to them saying so was me going "dope. thatd be nice i think. if i am someone new will show themself sooner or later".
and then like a number of months later i start having. very briefly. sudden surges of emotions to stimuli, emotions that felt distinctly foreign, and not-me to me. this happens before the new headmate actually properly awakens, basically like shes still cooking i like to say.
the first one made herself properly known now 6 months ago, while doing mushrooms on halloween. after that it took her a month or two to figure out how to communicate with me thru more than emotions and to take front.
the second one, is now a few weeks old, had a much easier time expressing herself, as figuring out communication was kinda a team effort she could piggy back off of.
hi sorry this got kinda long, i just rly love my headmates n im so glad theyre here and i like talking about them, idk i kinda lost track of what i was gonna say originally? this is satisfactory too tho, hope this helps still dgfhgg. but yeah the primary 'proof' that it wasnt just me talking to myself n making stuff up was like, those feelings i kept experiencing that i Knew were not mine.
every system is different tho yeah, noone but you can say what its like for you. it could differing facets of the one you, it could be entirely seperate individuals, it could be any range between or outside of that, or even in multiple ways at once.
i think the best thing if you suspect u identify w this community is like. keep an open mind, literally. dont dismiss any feelings outright, try to identify if theyre impulsive, intrusive, and/or maybe even just wishful thinking. its tricky, but you just gotta like. experiment, i think. if something is not right, you will often feel it in your gut that its not. just dont try to suppress something or someone, ive only seen that lead to hurt or even loss of headmates, work with them instead best u can