Balthazar doesn't like to think about what Castiel and that damned primate get up to when they're together with only each other and the ape's brother for company. He's never liked the Winchesters and he likes even less the way Castiel looks at them, and at Dean especially. The way Castiel talks about them like they're God's gift to the earth (though for all Balthazar knows, they might be, they did avert the end of the world) doesn't help. In fact, that makes it worse.
And Castiel does insist that the Winchesters have been there for him, have helped him through his times of trouble, were the ones to initially show him freedom and thrill, and that makes them a little more okay in Balthazar's book. Even if they do steal the attention of his favourite brother, and even if they do seem to lead danger and other unpleasant things around wherever they end up. And Balthazar isn't sure if they chase danger or if it's the other way around, and he doesn't care because the point is that the Winchesters are dangerous on top of being annoying and needy.
But he knows he doesn't have to like them because Castiel likes them and Cas' happiness matters.
But that doesn't mean he wants to think about Castiel and Dean might get up to. Definitely doesn't mean he wants to think about the way Castiel looks at Dean with such adoration. Really doesn't want to think about anything beyond just looks and hopes his favourite brother won't be getting up to anything like that. Not with that hunter, anyway. He deserves better as far as Balthazar's concerned.
No, he doesn't want to think about that at all and not thinking about it would be a lot easier if he only knew for sure. But he doesn't see Castiel half as much as he'd like to as of late and it's not like he's going to say anything to his brother, there's a war going on, he knows that. Things are messy.
Not that that makes it any easier, of course. Balthazar knows that when Castiel is off fighting, he'd rather be with the Winchesters. And Castiel doesn't know that Balthazar would rather have Castiel with him.
"Just spend a few hours with me, would you?" he asks just before Castiel departs.
And his brother turns back to look at him. "I can't. You know I don't have much time."
'Right. And even less for me,' he doesn't reply.