I haven’t used the feature where I inform Facebook of the relationship status of my friends, neither has my dad. Yet, he is now listed as my father. How is Facebook doing this?
My guess is it probably reads emails in the account linked to your FB. It might be reading other documents, cookies, or data on your hard drive as well.
I’ve had people accept my friends requests when I never actually sent one. I guess this is somehow happening because I hit the request button with out realizing it. (Prolly while putting the phone away in my pocket)
Maybe you or your father did something similar?
Facebook is definitely reading text messages. I met someone, exchanged two or three texts and Facebook was suggesting them as a friend two days later.
Do you have a sibling who might have told Facebook that he is her dad, and you are her brother? (Or a mom, or uncle or Aunt…)
Facebook hasn’t auto-filled any family relationships for me, even thoughi have several family members on Facebook.
I see no technical way for Facebook to read your text messages. The most likely explanation is that the person looked you up on Facebook, so Facebook offered to pair you up.
Facebook absolutely has the ability to read pretty much any data on your devices that it’s programmed to read, beginning with textual data like gmail and texts, but it might be able to ‘read’ other data as well. Most social media and big tech companies have cookies that can identify and retrieve geo-location data.
I still disagree with much of what you’re saying (in post #2 and this one). Not that I think Facebook wouldn’t like to process our e-mails and bank statements, but I don’t see how they could.
A Web page running in your PC browser is sandboxed and can’t read arbitrary files on your hard disk, or see what’s happening in other browser tabs.
An app running on your phone only has access to elements granted to it via the Android or iOS permissions – which is pretty far-reaching by default, including apparently text messages (though mine are off-limits). But GMail is not on the list of things the Facebook app can access.
Facebook requests access to contacts, phone, and sms for its Android app, but i didn’t give it access to anything but storage.
Facebook algorithms have a ridiculous amount of data if you have the app on your phone. They know who you contact, who you are in physical proximity with, who you call, etc. There are lots of patterns they can recognize and infer relationships from.
If I told you, I’d have to kill you. 
My FIL recently signed up for Facebook and isn’t very tech-savvy. He did it mostly to get his grandsons to shut up, but since then has also “friended” other relatives and a few real friends. He only uses it on his PC - no smart phone access involved. But could he have inadvertently allowed Facebook to access his email when he set it up, or clicked on a seemingly mundane request? Is there any setting or program feature that I should check for next time I visit to make sure his email(or anything else) isn’t compromised?
I know nothing about Facebook, so please excuse me if the answer is obvious to most people.
Just because you refused to grant facebook permission to access to your contacts, emails or messages doesn’t mean your dad did.
Your dad told Facebook you’re his son.
Facebook will request access to your contacts via your email to find other people you know on FB. To do so you need to supply your username and password via text boxes, so you can’t just accidentally do so via a single click.
Like Telemark says, you met someone, which means Facebook knows you two were in close physical proximity regardless of whether or not you were using the FB app at the time. That’s enough for their AI to recommend a friendship.
Yes, all this nefariousness about Facebook digging through your mail to somehow figure out that this guy is your dad is missing the most obvious answer: That one of you marked the other one as related and didn’t realize it or forgot.
While there’s plenty of reasons for Facebook to build tools to identify and suggest friends, there’s not much point in building a tool to automatically assign someone who is already your friend as your relative. Just looking at my own profile, neither of my parents are marked as related, even though there’s plenty of post where we’ve tagged each other and said things like “My dad and I.”
OK, thanks. I’ll check his settings/profile/whatever anyhow when I see him, just in case he thought providing his email info was necessary.
OK if you say so. I know I never told them, and my dad says he didn’t either, but I’ll just assume he did at some point and was unaware/forgot.