Depends on the Lucy.
Some people write Lucy as several years younger. In the first few eps Jimmy wants to ask her out. We find out the end of S2 that he's 20 so he's only 18-19 in the Pilot where Lois is 26 and Clark is 27-28.
In Learning to Love, I've written her as about 20 months younger and Jimmy as somewhere in between the two so Clark is definitely in the right age range.
I think most people write her somewhere in between 4-5 years younger but there's no hard/fast rule as to how old she is since it's never TRULY addressed in canon. We assume she's about Jimmy's age because he wants to ask her out.
To shamelessly self-promote... my
Sister Switch has a married Lucy and Clark but... that's all I'm saying about that
.
Carol
