From Scientific American:
Nicholas and his wife, Erika, like to joke that they had an arranged marriage, South Asia–style. Although they lived within four blocks of each other for two years and were both students at Harvard, their paths never crossed. Erika had to go all the way to Bangladesh so that Nicholas could find her. In the summer of 1987 he went to Washington, D.C., where he had grown up and gone to high school, to care for his ailing mother. He was a medical student, single and, he foolishly thought, not ready for a serious relationship. His old high school friend, Nasi, was also home for the summer. Nasi’s girlfriend, Bemy, who had come to know Nicholas well enough that her gentle teasing was a source of amusement for all of them, was also there. She had, as it turned out, just returned from a year in rural Bangladesh, doing community development work.
In the wood and tin hut where Bemy had spent her year abroad was a beautiful young American woman with whom she shared both a burning desire to end poverty and a metal bucket to wash her hair. You probably know where this story is going. One afternoon, in the middle of the monsoon, while writing a postcard to Nasi, Bemy suddenly turned to her friend Erika and blurted out: “I just thought of the man you’re going to marry.” That man was Nicholas. Erika was incredulous. But months later she agreed to meet him in D.C., and the four of them had dinner at Nasi’s house. Nicholas was, of course, immediately smitten. Erika was “not unimpressed,” as she later put it. That night, after getting home, she woke up her sister to announce that she had indeed met the man she was going to marry. Three dates later Nicholas told Erika he was in love. And that is how he came to marry a woman who was three degrees removed from him all along—she was connected to him through two intermediate social ties, a friend of a friend of a friend—someone who had lived practically next door, whom he had never previously met, but who was just perfect for him.
More here.