Prince: No Free Rides for Wannabe Relatives ... If Estate Gets Its Way

All the so-called "long lost" relatives of Prince should have to pay to prove they're truly the singer's blood ... according to the bank running his estate.

TMZ obtained docs filed by Bremer Trust Bank ... and it's asking a judge to sign off on getting anyone who's "claiming a genetic relationship" to fork over the dough to cover DNA testing costs.

As we've told you ... at least one man has come forward claiming he's Prince's son and says he's ready and willing to get genetic testing to prove it.