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.