ASWAD KHAN DIDN'T understand why people were congratulating him. 

 On a February morning in 2017, rolling out of bed at his home in an upper-middle class area of Karachi, Pakistan, Khan saw a flurry of text messages, mostly from old college and high school friends, many living in the United States, that had arrived the night before. They were wishing him well about some good news that he had not yet received. Groggily, he scrolled through his phone and scanned the messages.

Khan, then age 31, soon came across a text that revealed what was going on. "Congrats bro your best friend is getting married!" the message read. "You must be so happy man."

He could not believe what he had just read.

Khan immediately logged onto Facebook to check the page of his childhood best friend, Ahmed. He quickly realized that Ahmed had unfollowed him and restricted his access to the profile. Meanwhile, the pages of his other friends were congratulating Ahmed on his engagement and the wedding that he had apparently announced for that summer. Ahmed, whose full name is being withheld at Khan's request and who did not respond to requests for comment, had shared every moment of his life with Khan since they were kids. Yet he had not even told Khan about his engagement.