Chris wishes they could just come out properly. Their families and close friends know, and he suspects that some of the younger cast members have figured it out. He's caught them whispering and giggling several times, but they always shut up when they see him there.
Their publicist also knows. And he's strictly forbidden them from saying or doing anything in public that could get it in the papers. He's afraid of alienating all Chris' (and especially Sean's) teenage fangirls.
Sometimes, Chris hates being Percy.
Still, he knows Sean loves him, and for now, that will have to be enough.