In "Ides of Metropolis" Lex recalls hiring Henry Harrison for LexCom, who then worked for him for 20 years before being fired within a month of being eligible for retirement with full pension. This means that Lex started LexCom either when he was very young (early 20s), or that he himself in his late 40s, early 50s. Taking that into consideration, let's discuss what we learned about Lex from his two sons. Lex Jr, was already discussed, but Jaxon Xavier was born Nov 12, 1962 according to VD, making him 3.5-4 years older than Clark.
If Lex had Xavier when he was 20, Lex would have been at least 49 in 1993, when the series began. If Lex Jr was older than that, then Lex had to be at least in his early 50s at that point and probably twice Lois's age.
