sometimes when i know a person really well/care about them/love them and they talk about themselves in the past, it makes my body react the same way it does when i feel abandonment or sudden loss??? it’s like an involuntary feeling like “i suddenly don’t know u, what are u saying, what do u mean?” and i can’t picture them in the past because i only know them now. so when my friends/partner talk about themselves in the past, it makes me super uncomfortable and this has always happened and i don’t know WHY. i know i get feelings of dissociation sometimes but i can’t find out if it’s part of that online anywhere :/ i talk about myself all the time, in detail, about my past and present and it doesn’t do a thing to me. but when other people try to tell me about their past i get so scared, like i’ve lost them or they died. like, a pang of fear like i suddenly don’t know where they are. it makes me so angry with myself. it also gives me a feeling of jealousy like "i don't know what ur talking about bcus i wasn't in ur life then, i wasn't there, and i'm jealous of people who were there to see u then". and it's REALLY weird and i don't understand it at all. it isn't a voluntary thought. the anxious feelings i get when my boyfriend talks about stuff in his past, especially bad times he's had, come on me like a train and i have to try and stop it with a butterfly net. feeling that level of anxiety about something so random and inexplicable makes me worried about myself.
I don't know if it's dissociation but it sounds like anxiety triggered by the ambiguity of other people's pasts. Ambiguity is a common trigger for anxiety. And in the case of your loved ones, I guess because you weren't there and don't know exactly what went on, it's causing you distress because these things are totally beyond your control.
that is something i deal with too!! i wish i understood more the root. mostly, like you mentioned, it is definitely beyond my control and i have a hard time with control. not in a creepy abusive way, i don't wanna control people, but i wanna be able to control myself and my own emotions and sometimes others' behavior sends me into a tailspin of confusing thoughts.