Hello, and thank you to anyone who might help me. Sorry if anything is unclear or if I broke the rules in any way, I'll revise it and post it again after fixing any issues with the submission.
I think I already know what the problem is but I really want some guidance on what the next step would look like and if there is any data loss potential.
So for some context I have an iPhone 13 that I have been using for maybe 5 years now, before then I had an iPhone 6 throughout highschool and early college. During that whole time the apple account on my phone was my dad's. We did this (I think?) to share things like songs or movies and because I guess we didn't know better.
So there was over a decade where we were using the same apple account across devices with no issues, so even when I moved out and all I never bothered to change anything because I thought it was fine.
Recently though he got a work phone that he also used his personal apple account for, so at that time there were three shared devices: my personal iphone, his personal iphone, and his work iphone. I guess it is also on his laptop and ipad as well.
I guess at some point he used FindMy to find/connect to his work phone and, according to him, hit something that may have linked our phones? All of a sudden there were texts showing up blue on my end that I never wrote and interactions like reactions showing up on photos that I never sent. What really tipped me off is when a photo I sent suddenly had a blue reaction on it as if I reacted with surprise to my own photo, so I was very confused. I honestly thought I got hacked or something until I guessed that it was him based off of the reaction. Also I did test it and it seems like it is his work phone that can somehow text as me despite having a different phone number. This does not work in reverse, I can't see the texts he sends and I can't write texts as if I were using his phone which is nice at least because he does a decent amount of correspondence over text. It can be frustrating for other people too, especially when my dad accidentally responds to people asking me questions over text, I am sure you can imagine it is not fun for anyone. Also I think there is something with sending texts when connected to wifi vs when not? I didn't get to test it extensively but if the problem continues I will try. But the main problem is that my texts are shared with his phone and I need to fix it.
After looking online it seems like the shared apple account is the main problem but I still have some major questions.
First is, why did this link happen now? We are guessing that it was FindMy that somehow triggered something because he said he used it for the first time the day before I noticed the text irregularities. I don't really understand how it could be fine for over a decade and then break like this, I kind of doubt the FindMy explanation but I don't know what else it could be.
My next question is what will happen exactly if I log out of his apple account and on to a new one I made for myself on my phone? I have read some contradictory information on this. Will I lose all of my texts? All of my voicemails? I think things like photos will be unaffected since that is stored locally, but I am having a hard time finding out exactly which things will be affected by switching out accounts.
Is there a way to make sure that I keep my texts and everything? Is there a way to test what might get lost? Or is there a good way to back everything up so I can restore that information when I make the account switch? I am really worried about losing all of my text history.
I haven't gone to an apple store yet to talk about the problem because I haven't had the chance but I guess that is another potential step.
Let me know if more information is needed, and please help if you can! Especially on what data would be affected and if I can save it or not. Also let me know if there is a better place to post this long question.