Brainz

"Divorce clustering" subject of researchers from three North American universities.  Sociologists and psychologists led by Dr. Rose McDermott of Brown University in Rhode Island found that any divorce causes a ripple effect through families, friends, and even work colleagues. Dr. McDermott and her team studied 12,000 couples from 1948 living in in Framingham.  The team found a direct link between knowing divorced people and the risks to a marriage.  Dr. McDermott reports that that is a "person to person effect" and that the "full network shows that participants are 75% more likely to be divorced if a person - obviously other than their spouse 0 that that are directly connected to is divorced.  The size of the effect for people at two degrees of separation, for example the friend of a friend, is 33%.  At three degrees the effect disappears." 

Dr. McDermott and her team also found an increase of divorce rates among family members and co-workers increased the odds of a marriage ending.  The researchers also found a 22% increased chance of divorce if a sibling had divorced.  Couples with children were reportedly "less susceptible to being influenced toward divorce." 

The study concluded that the number of divorced people a person knows leads to an increased risk in his or her own marriage.

The phenomenon has been aptly titled "divorced clustering.