Kashmir Hill, reporting for Gizmodo: Rebecca Porter and I were strangers, as far as I knew. Facebook, however, thought we might be connected. Her name popped up this summer on my list of "People You May Know," the social network's roster of potential new online friends for me. [...] She showed up on the list after about a month: an older woman, living in Ohio, with whom I had no Facebook friends in common. I did not recognize her, but her last name was familiar. My biological grandfather is a man I've never met, with the last name Porter, who abandoned my father when he was a baby. My father was adopted by a man whose last name was Hill, and he didn't find out about his biological father until adulthood. The Porter family lived in Ohio. Growing up half a country away, in Florida, I'd known these blood relatives were out there, but there was no reason to think I would ever meet them. A few years ago, my father eventually did meet his biological father, along with two uncles and an aunt, when they sought him out during a trip back to Ohio for his mother's funeral. None of them use Facebook. I sent the woman a Facebook message explaining the situation and asking if she was related to my biological grandfather. "Yes," she wrote back. Rebecca Porter, we discovered, is my great aunt, by marriage. She is married to my biological grandfather's brother; she met him 35 years ago, the year after I was born. Facebook knew my family tree better than I did "I didn't know about you," she told me, when we talked by phone. "I don't understand how Facebook made the connection." How Facebook had linked us remained hard to fathom. My father had met her husband in person that one time, after my grandmother's funeral. They exchanged emails, and my father had his number in his phone. But neither of them uses Facebook. Nor do the other people between me and Rebecca Porter on the family tree.