I never heard that theory before. Did Stanley Ann ever even meet Mr. X?
It’s been floated for some time, but based on obvious traits, it’s highly unlikely. Malcolm was lighter than Zero, and with an even Whiter woman, any children more than likely would’ve probably passed for White. If Barack, Sr. was not the bio dad, it would be Frank Marshall Davis. At least the complexion would be about right (Sr. might’ve been too dark to have fathered Barry).
Other than for Malcolm’s earlier years as a street hustler who also “serviced” older White men, I think after his conversion, there were no particular hints of sex scandal. Even they alluded to that in Spike Lee’s movie that compared to MLK, Malcolm was a “monk” (when they were surveilled by the FBI). I can’t see that Malcolm would’ve been in a situation in 1961 where he’d have been alone in a room with a White teenaged girl.