referring to the story "But I'm Stronger" by Gina Blank. Lois is not older than Clark, is she? I mean, if she was born in 1967, and he in 1966, that makes him a year older.
No, she's not, but we didn't find out Lois's birth year until the end of the third season, so authors who wrote fanfic before that time wouldn't have had that information. I can't place the story you are refering to just from the title, but I think Gina was an early author.
Since Teri is a year and a half older than Dean, some authors went in that direction for Lois, as well, before we found out her exact age. (FYI: The UK version of the pilot gave Lois's age as 26, but the US version didn't, so that, again, wouldn't have been any help to early authors.)
Kathy