You, Dean, Sam, and Bobby are a pack. Dean and Bobby are Alphas, Sam the beta, and you are the Omega. They both take care of you and protect you while you, in return, tend to them and care for them. No demon or monster is stupid enough to go after you. Dean and you aren't mates, he considers you as his little sister and you consider him your big brother. Bobby is the father figure.

And then Castiel came into the mix. Instantly, the pack was sent on high alert. With how often he appears and leaves for Heaven, you can't get a good whiff of his scent, which sets you off. Dean, Bobby, and Sam are wary because he's an angel and an alpha. They rely on you for pack decisions, knowing that you are more adept at handling that.

Bobby is out on a hunt while Dean, Sam, and you are in the bunker. Castiel teleports in and starts speaking with the boys. You decide it's time to finally get his scent and add him to the pack.