Let's say we have 3 people on Facebook: person A, person B, and person C. All 3 people have been using Facebook for a few years.
Let's say person A and person B have been friends on Facebook for two years. Person B then changes his relationship status to "in a relationship with 'person C' ". A and C have never been friends, and person C was never visible to person A (when searched for in the search bar) prior to person B's relationship status change (nor visible to person A on person B's friends list). After the relationship status change however, person C is now visible to person A (shows up on the search bar when searched). Person A also now sees person C on person B's friends list even though they have never seen person B add person C as a friend (person A has never seen the usual notification that person B is now friends with person C). How would this be possible?