Juice finally addressed the conspiracy theory that's been floating around for decades ... that he secretly knocked up Kris behind Robert Kardashian's back 34 years ago -- and the family has been covering it up ever since.
So, when he was out in Vegas over the weekend -- a photog asked if congratulations were in order regarding Khloe's pregnancy.
Simpson clearly understood the subtext -- and replied, "Well, for Bob, God bless his soul, yeah. I don't know for me. I don't think for me I have nothing to do with it."
He added, "I would be proud ... but trust me, I had nothing to do with it."
Meanwhile, watch O.J.'s daughter, Arnelle, in the background -- she's CONVINCED her dad's no Kardashian creator.