Katherine Schwarzenegger Gushes Over Chris Pratt ... Half Bro Joseph Baena Likes It!!!

Katherine Schwarzenegger's praise for fiance Chris Pratt is obviously something their fans are here for, but one "like" in particular stands out among tens of thousands -- the one from Joseph Baena.

Katherine's brother from another mother made it clear he's a fan of her engagement to Chris Friday, with a double-tap on her IG post. Kat was shouting out Pratt and encouraging fans to go check out his new film, 'The Lego Movie 2.'

Joseph's "like" could signal a big shift in the House of Schwarzenegger. As far as we know, Arnold's kids with Maria Shriver -- Katherine, Christopher and Patrick -- have never had a relationship with Joe ... whose mom is the housekeeper with whom Arnold had an affair.

It's possible they've connected away from the spotlight -- or it could just be that Joseph's using social media to extend an olive branch.

As you know, Chris and Katherine are planning their wedding right now ... so maybe's Joseph's got a shot at an invitation after all.

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