Just change your number. You wrote this for yourself, and we've read it, heard it, and believe it. Nothing you do will change them, so just change your number

I would seek a therapist to help you through family issues. No Internet strangers are going to be able help, and sending a passive aggressive text to everyone and then running away is not going to help either.

I just wanna say it's OK to cut contact with abusive people.
I'm sorry these people are shit, you deserve better.

Change the number, seek out therapy, get your issues under control, and decide what to do next. If the other victim doesn't tell you themselves, you have no reason to know who they are or what happened. If you think you were sexually abused, seek therapy and the police.

Perhaps after seeing a therapist, some day in the future you'll be in a position to communicate your feelings to your family or maybe you'll find it isn't worth it. But if your family situation is adding to your problems, step away silently and work on you. You don't need to announce your departure, just leave.

Send it if you live at your own, don't need to change sims card you can block anyone who complain, if you live inside their roof so no, wait until you got independent enough

What you’re doing is not easy, and I admire your strength. I wish you the absolute best!

Cut off from the family first. Be in a position where no family member can contact or reach out to you, or you can reach out to them. Then send the message.

Agree with other commenters here in that writing it and sharing it is important, but probably everyone in that list will agree with what you say about the others, but completely shrug off whatever is aimed at themselves.

One useful place for that letter might be in using it as a public reply everytime they message you or mention you online, so others might be able to take it as a warning or validation for their own interactions with them, but as a direct hit on their ego it will just be met with deflection and justification. At minimum it might make them avoid you instead of you having to avoid them online.

I just want you to be aware that you might not get the response that you're hoping for/secretly wish you'd get. I sent a letter like this once to my dad and brother and they both laughed and threw it back in my face; I sort of expected it but I'd thought that my mum would be bemused but supportive. She wasn't.

Good luck anyway, I hope you get the closure you need!

I agree with one of the other people; make sure that you're in a position where they have no ability to contact you, and you will never need to contact them, and then send it. That means things like a new address in a new city, making sure that they're not on anything like student loans, etc. You may need to cut a lot of other ties as well; abusive families tend to use friends of their victim to keep tabs on them. Really severing ties in a way that is very, very hard for a determined abuser to track is hard, but i'd suggest taking as many of those steps as you can prior to throwing that particular bomb into a group chat.

PS - I think that you can go farther with you dad. There are a lot of great quote from Jesus--assuming that he's Christian--that would be appropriate.