Lois discovers that she is not the oldest child - she has an older brother that she never met.
Okay, this is something I actually want written. I can't remember which script it's in but there's a goof of Lois mentioning her brother so there's legs for it... I think it's the Christmas episode season 2 because she was listing out reasons why she hates going home to be with her family on the holidays and she mentions it. Plus it'd be super fun to see a big brother being overprotective of Lois and not liking Clark one bit.