What house storing to you have for the other characters outside of Dean and Cas, like Charlie, Sam, Kevin etc?
Wow, hmm, interesting question.
There’s not as much material for Charlie or Kevin, but I would call at least one of their Houses Hufflepuff. I haven’t watched their pittance of episodes with this in mind before, but I could tell you more after having done so. I have suspected before that Charlie’s second House could be Gryffindor, and Kevin’s Ravenclaw, but that might change.
Sam is a Slytherdor, or a Slytherclaw. Why? Because Sam’s ambition outweighs everything except what he was conditioned into (except in the case where he makes that conditioned duty his ambition): Slytherin. In addition to the things I’ve said to explain Castiel’s Slytherinness, Sam doesn’t come back to Dean out of chosen loyalty necessarily, he comes back out of obligation if not ambition: “I have to find Jessica’s killer”. And it’s most of the time treated by him as temporary, till he gets back to what he wants to do.
Sam went to college despite what his father wanted him to do. We see Sam reading, for pleasure and for work, constantly. He’s always learning, always picking up new stuff, and it’s enjoyable for him, he seeks it. He doesn’t take up research; he instigates it. Ravenclaw. Not to mention Sam’s biggest arc is a desperation for knowledge about himself (five seasons of “who am I? I’m the one who saves the world by self-destructing”). And then, there’s Gryffindor in him, because of the way he and Dean both throw themselves into the fire, as well as the way Sam is obsessed with being Good, not doing Good, necessarily, but being Good (like, think of S2 when he’s like “what if I become Evil, you have to kill me Dean” which Meg then reiterated in 2x14 when she was playing Sam convincingly) though unlike Dean’s throwing, Sam’s is tempered by “only if this is what I have to do” (Slytherin). I go back and forth between the two. I definitely don’t see a bit of Hufflepuff in Sam, tbh. Sam’s loyalty is extremely Slytherin.