Tess squares off against Lionel on the episode "Scion." They battle over the name Luthor.
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It's Conner Kent! As this photo makes clear, the character played by Lucas Grabeel will be revealed to be Superboy on a final season episode of Smallville.
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Smallville Season 10 Episode 16 Quotes

Lionel: You can't hide Alexander from me forever.
Tess: I'm saving him from an encore performance of Daddy Dearest.

So it's not just the Luthor males who like secrets.

Lionel