#two pillows

His

Sam before Dean moves in with him:

1. Sleeps at center of bed

2. One pillow

3. mattress looks hard

Sam after Dean moves in with him:

1. Sleeps at right side of bed (and obvious empty spot at left side)

2. two pillows

3. Mattress looks softer (memory foam that Dean likes)

And about bed side preference, you can see below that Dean prefers the left side

Also through their times in motel bedrooms, they unconsciously formed the habit of Sam on right side and Dean on left side (see below)

Sam has had only one pillow on his bed for the past like 5 years. Season 11 has like at least five scenes clearly showing one pillow.

It doesn’t show up much in season 12 but most recently in 13x21, Sam very clearly has one pillow here.

We haven’t seen Sam’s room since then, until now, 15x03:

Get out, Emily.

Johnny Cousin is a failure, and he knows it: his fanciful dream of an illustrious career is fatally flawed, and it only remains for him to acknowledge the fact. His admission, when it comes, is surprisingly subdued despite the thunderous cymbal crash that precedes it. Surprising also because the eruption of anger against the outside world is followed by an all too fleeting glimpse of introspection - and Johnny recoils in horror. For one brief moment, his primary concern is not his own gratification but the sanity of the one human being who does love him unconditionally, and whose happiness is in his gift.

Like that's my problem with the idea of canon Wincest. Obviously there wouldn't be a sex scene anyway, but if there was, I can't actually... picture Sam doing with Dean what he does with his partners onscreen. I can't picture Dean behaving with Sam the way he behaves with his partners. The whole point of sex for both of them seems to be behaving in a way that they don't around each other.

But when I was thinking that just now, it occurred to me how this season Dean has shown emotional vulnerability to Sam that he's almost never exposed before. The end of Proverbs 17:3 being the best example.

Is it related to the two pillows on Sam's bed? Is it another hint that the nature of Sam and Dean's relationship has changed or will change in the near future?

Probably not.

But it's certainly a strong step in that direction. If in 5 months we get any kind of confirmation of canon Wincest whether it's something in the last episode or J2 saying something at a con then I'm going to count that scene and similar ones as a hint that Sam and Dean were exploring a new dynamic between what we saw on our screens.