Broken family ties and pregnant

Ma

So I have a big sister who is 16 years older then I am and since I was little she always had on and off contact with our mom and me in the middle until a few years ago when she suddenly ghosted me as well while nothing happend. In those same turbulent years she divorced her husband who she has two kids with and I haven’t seen any of them since and today I got a friendship request from him out of the blue on facebook.

I was figuring maybe it’s for the kids because they maybe found out that I’m pregnant due to a public fb post but I’m hesitant to reply since I’m afraid of inviting them into my life again and I don’t want myself or the kids to get hurt like I did when I was little and felt my family was always fighting.

What would you guys do? Accept/ignore or what?

(My first reaction is questioning if this is for real I’d rather get a message or call instead of this akward friendship request. In which I don’t know their intentions.)