Bio Dad #2 -- MJ Baby Mama Is 'Crazy'

The parents of another man Claire Elisabeth Fields Cruise named in today's wacked out press conference say their son, Christopher Caputo, did once date the "unstable" woman -- but it's "totally impossible" for him to be the father of any of Michael Jackson's children.

Caputo's 'rents tell TMZ the two dated when Chris was 16-years-old. They believe Cruise had "mental issues" back then and was "fixated" on their son.

Chris is now 44 and he hasn't spoken to Cruise since high school.

FYI -- On her MySpace, Fields also says she's the "biological mother" of Brad Pitt, all his children, Gisele Bundchen, Leo DiCaprio, Anna Nicole Smith ... and she ran for President in 2008.