We get this question so often, we thought it deserved it's own blog post. Here at J&J we have a carefully curated list of photographers with whom we have reciprocal agreements. If we are too sick to photograph a wedding, they will step in to photograph it and if they are too sick, we will photograph it.
These photographers are all working pros with full service studios. We would not trust your wedding to a hobbyist or amateur. All the professionals are carefully screened, carry professional liability insurance, and are professionals who's style and angles are similar to ours. These are professionals we would trust to shoot our own wedding.
We keep a small list of 10 such photographers in the area where, in the event of a sickness/accident/death in the family/etc, we would email that list and be able to find a professional photographer to photograph your wedding.
This has never happened to date in all our years of photographing weddings (and hopefully never will). However, rest assured that we have policies and procedures in place so that even if the unthinkable would happen, we have extensive backup plans to make sure your day goes off without a hitch.