Will getting married during Mercury retro lead to divorce?

Found out former coworkers whom I haven't seen in a couple of years finally got married on Saturday. They've each been married before and had dated for several years. How would Merc retro affect their marriage? Is there a general rule?

The rule is that if you marry someone with whom you are incompatible the marriage will fail at some point.
The issues with a ret. Merc might affect "the wedding", not the marriage.
LIN