Lawyers for Katherine Jackson have been nosing around ... trying to find out what Debbie Rowe might say under oath about the paternity of the two kids she bore while married to Michael Jackson.
Sources connected to Katherine tell TMZ ... her lawyers have been making a number of inquiries on the eve of the family's wrongful death trial against AEG Live.
We're told lawyers worry Debbie will testify Michael is NOT the biological father of Prince and Paris. TMZ broke the story back in 2009 ... Michael indeed is not the biological father.
Debbie is on the witness list for both Katherine and AEG Live. AEG has taken Debbie's deposition but -- shockingly -- we've learned AEG never asked Debbie a single question about paternity as it relates to MJ.
As for why Katherine's lawyers are so interested in Debbie's testimony ... she's the one who knows the most about MJ and the paternity, and they're worried AEG may try to prove the kids don't have any legal ties to Michael, which could torpedo their damage claim.
Katherine's lawyers have already filed legal docs asking the judge to exclude any evidence of paternity. The judge has yet to rule on the motion.
In the end, none of this may amount to anything because under California law ... when a woman gives birth while living with her husband, the husband is conclusively presumed to be the father, unless he's sterile or impotent.