It's the best that Sam could hope for. Because, really, he did like Castiel. And, if nothing else, wanting to become his friend might not be the best path to mating, but Sam's more concerned that Castiel makes a good and happy match rather than being railroaded into something he doesn't want.

Which is something Zachariah should be thinking on more, honestly. Omegas who aren't happy or at least content with their situation don't have children, after all.

He smiles widely, though, and takes Castiel's hand, covering it with both of his own in a display of warmth. "I look forward to getting to know you better as well, Castiel."