According to political scientist Rose McDermott and colleagues, kind of. By examining divorce and social networks among participants in a heart health study, they found that a person whose friend or sibling gets a divorce is more likely to get divorced. Even friends-of-friends have this effect, though neighbors do not. Having kids appears to mitigate the influence of other people's divorces somewhat, and people who are popular — who are considered a friend by lots of other people — are less likely to get divorced at all.
The study authors write that the "contagious" nature of divorce is unlikely to be caused by shared environmental factors (they mention "local counseling resources, local churches, or local norms") because friends who live far away are just as influential as those who live close by. Non-environmental factors like shared values or stresses seem more difficult to control for — but the study authors say they've dealt with this possibility too*. It's not just that people in the same groups lead similar lives, they conclude — we can actually change the lives, and relationships, of our friends.
McDermott et al write,
Romantic and sexual practices as diverse as contraceptive use, sexual behaviors, and fertility decisions are all strongly influenced by the existence of these behaviors within one's network. So divorce fits in with a pattern wherein such seemingly individualistic and intimate matters are in fact partly determined by collective, social network processes.
That is, even such an ostensibly private and unique thing as a marriage between two people is profoundly influenced by the groups to which these people belong. This actually makes a lot of intuitive sense. In one way, romantic relationships (here I should note that one of the study's acknowledged limitations is its focus on heterosexual unions) are totally individual — I firmly believe that nobody really knows what goes on between a couple except the couple themselves, and it's always surprising to see who stays together and who splits apart. But what your friends do can influence not just what you think is cool or acceptable, but what seems okay, survivable, possible. A friend who gets back on her feet after a breakup can show that the end of a relationship isn't the end of the world — and that you might have someone to commiserate with should you decide to end yours. These effects aren't just mindless lemming behavior — as the study authors note, social support is important after a divorce (interestingly, especially for men), and when making a big decision, it makes sense to see if anyone has gone before.