19The Age Difference
Grey's Anatomy isn't always great with timeline continuity. Just look at the confusion around the newest Grey sibling, Maggie, and her supposed age. The gap between Mark and Lexie's ages could be even larger than the sixteen years that was established during season six, but the
current canon is that Lexie was born in 1984 and Mark was born in 1968. A twenty-six-year-old dating a man in his early forties is way weirder than the kitschy jokes that the show would occasionally make about Mark dating "Little Grey," but as the seasons went on, the size of the age gap got buried under more dramatic issues like plane crashes, infidelity, and surprise pregnancies.