Justin Herbert and Jaxson Dart might as well break up with their girlfriends now … because a famed astrologist says their relationships aren’t written in the stars.

Richard James — host of the “StarCast Weekly” show — starts out by breaking down the Los Angeles Chargers star QB’s relationship with his pop star better half, Madison Beer … which Richard says is unlikely to work out because they’re both Pisces.

Plus, James isn’t sure the two are sexually compatible … arguing that because Herbo’s Mars is in Aries, he’s more sexually spontaneous … while Madison might be a bit freakier but ultimately looking for something more long-term.

As for Dart — who is dating model Marissa Ayers — James says the Giants’ QB is attracted to her confidence … but communication is key here, and the stars dictate they have a giant issue there.

Both the Chargers and Giants are out of the playoffs … so, they’ll have to wait until next year to win it all … and wait until their next relationship to find happily ever after, if James is right.