Jax Taylor may be the No. 1 guy in the group … but that didn’t stop him from getting hit with divorce documents while filming season 2 of “The Valley” … TMZ has learned.

Sources connected to the show tell TMZ … the Bravo personality was served the docs from his estranged wife, Brittany Cartwright, while filming the new season of the reality show Tuesday.

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We’re told both Jax and Brittany filmed for “The Valley” Tuesday … however, they did not film together — which means a 3rd party brought the documents to the Jax’s Studio City sports bar owner (and former bartender at the restaurant SUR).

Sources connected to the couple tell TMZ … Brittany took the initiative and decided it was time to file … since her estranged hubby has done too many things for a reconciliation to occur.

No word on what exactly went down between the former flames … but sources say Jax is getting ticked off from all the praise Brittany’s getting for choosing to file — especially as he thinks Brittany has her own dark side to her.

Jax may not be the true villain in this split … we’re told all will be revealed when “The Valley” returns for its sophomore season … we’ve been warned it’ll be a “heavy one.”

Relationship issues aside, Jax and Brittany are simply focusing on their young son, Cruz … who has their full attention now that the day-to-day chaos of their marriage is no longer distracting them.

We’ve reached out to reps for Jax and Brittany for comment … so far, no word back.