It's going to be a real battle to see who's going to be the best man at Castle (Nathan Fillion) and Beckett's (Stana Katic) wedding on Castle.

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Both Ryan (Seamus Dever) and Esposito (Jon Huertas) will be competing to be the best man to Castle at his wedding, and they may stop at nothing in order to claim the position, according to a new spoiler report by TV Guide.

"Ryan [wants] to have nice time at the bachelor party," Dever told the publication. "He knows a great place with a great wine list. He's going to be a classy best man where Esposito is going to be like, 'Yeah, I'm your frat boy!'"

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However, all of their efforts may be in vain as Castle is blissfully unaware.

"The whole time they're jockeying for favor, all of their efforts are wasted because he's not even aware of what they're trying to do," Dever teased.

It is not known when the big best man competition will go down, but there are only three episodes left of season 6, so fans should expect it very soon.

The season 6 finale of Castle is titled For Better or Worse, implying that the episode will focus at least somewhat on Castle and Beckett's impending marriage. Though it is not known if they will go all the way and get married in the finale, new reports note that they will be coming "one step closer" to getting hitched.

Castle season 6 airs Mondays at 10 p.m. on ABC.

Watch a promo for the next episode of Castle here: