There's a very slight shift in Sam's demeanor when Zachariah speaks up. Sam may be the only Alpha in the family since his father's death, but he's used to the posturing. He casts a glance to Zachariah, then turns his body so that he is very obviously paying attention to Castiel and not the other man.

If Zachariah wants to get into it with him, he can. But Sam is here for one reason and he's going to pay attention to Castiel instead.

"We did, yes. Her Alpha father was planning to market her off to the highest bidder. My brother and I were only too happy to be responsible for bringing him in and making certain the girl was all right." Sam smiles and shrugs. "Everybody deserves a chance to marry who they want to."