Family from nowhere

So just as I'm sitting through another one of grandmas sagas, trying for dear life to sift through the irrelevant bits to the heart of her story, I get a message from a stranger on Facebook. Donkers- seems to me a familiar name, so I ask grandma. No, she says, "that doesn't sound like anyone I know." so I hesitatingly accept the friend request and poke through this persons profile. His siblings are...? His mothers name was...? And I read a few other clues that I thought might be helpful and all of a sudden she perks up and says, "oh! That must be so and so's son! He was cousin of- and he was the son of-!" the list goes on for 10 minutes! So I write back to this stranger and confirm the pedigree and presto changeo, he is family now. I think that timely connection has grown grandmas interest in Facebook, but how many hours will it take to show her the ropes again?