Family research [ CW : War & WW2 events mentioned slightly ]

To lay out basic things, my bio Father (46? M) hasn't really told me (18yo ftm) ANYthing about the family history on his side of the family while my mum (early 40s they/them) and their side of the family has happily told me everything up to my late great grandfather working on farms & grandfather's brother being in the Vietnam War Air Force.

The only thing I know from bio father is that: 1. Family members was survivers of the h0l0caust (im not sure if I'm allowed to write that uncensored or not im so sorry) 2. I could get medical issues like he has 3. I have younger sisters from him who are twins. Nothing about his mum's side of the family nor his dad's. I only know his mum & sisters.

Here's the thing: I cut off Bio Dad and his Mum. Completely after a fall out over past stuff and family drama I don't wanna dig out. I don't wanna contact him nor his side of the family so I'm going in this blind as a bat playing "I don't know who that is". Its like an ARG but family style, sure I can ask one of my aunts but it'd be awkward going "Hey so, don't tell Bio Dad that I contacted you because me and Bio aren't on good terms." Then proceed to ask for family history.

It feels rude, it feels odd just randomly messaging on Facebook out of the blue. I need help and advice on this.

(I am so sorry if there's any confusing sentences. I am dyslexic and I'm writing this running off on fumes of sleep. Again I am so sorry for the censoring- I don't know if it is okay, most places don't like it:'D)