I love the way you write Sirius's and Remus's relationship here, with Remus being so observant of Sirius's feelings and offering to help him, and Sirius being grateful but also a little put out that Remus is in full-on professor mode. I think my favorite thing about the story is how Sirius's worry about the household things is a metaphor for a larger fear, that they are getting ready to leave the safety of Hogwarts and face the war that is raging outside. I also adored this part:

Sirius splutters ineffectively as he searches for a viable objection, but Peter interjects before one occurs to him. 'You two argue like an old married couple.'

As James agrees wholeheartedly and dissolves into a tangent of comparable days past with Lily, Sirius catches Remus' wink and smiles like a smitten first year girl.

And the coming out scene—James's indignation that Remus isn't attracted to Lily was priceless, and I loved how Sirius puts and end to the discussion in a perfectly Sirius way:

'Me,' interjects Sirius, walking up behind Remus and wrapping his arms around the boy's waist. 'I'm his type.'

And the ending was just lovely and bittersweet and perfect.