Even from the beginning - before TMTB screwed up everyone's bio - it doesn't say anything about a father for either of them.
The highly inaccurate CSI Companion states:
"Catherine was born in Las Vegas to a single mother, a hard-working cocktail waitress at the big casinos. Her mother, looking for a better place to raise her two daughters, moved around the West Coast for much of their teenage years."
ETA:
God, I could only wish that fanfiction was the actual show. Then I'd have a smile on my face more these days, instead of the grumpy frown.