This would be INSANE if it were true, but it's probably not:  The "Star" tabloid claims that RIHANNA and KARRUECHE TRAN are racing to be the first one impregnated by CHRIS BROWN.

 

 

--They both have their own reasons to get knocked up by Chris:  Rihanna is hopelessly in love . . . and Karrueche sees him as a sugar daddy