Two (Three?) Men And A Baby

On an unfortunate hunt, they find Cas dead cradling a baby. Dean is immediately swamped by sadness, but takes the baby without question as his own. Sam falls into denial and depression. Later, when the kid starts talking, he points at things, and even though it's sometimes weird, he's always right. (Cat, car, sign, tree, rock, etc.) and one day he points and says "man" and he keeps doing it until he says what he really means.