What secret did Mark Lee and Jan Davis keep from NASA while training for a space mission?

In January 1991, a couple of crazy kids got married. That these particular “kids” were in their late 30s, were astronauts, and were keeping their marriage a secret from their bosses at NASA only added to the romance. Mark Lee and Jan Davis met during training for a space shuttle mission and kept their relationship quiet long enough to ensure that it would be difficult to replace them on the mission, as NASA normally would have done under its then-unwritten rule that banned married astronauts from flying together. And so, in September 1992, Lee and Davis became the first (and, after the unwritten rule became a written one, possibly last) married couple in space.