I really enjoyed this. Minerva/Severus is one of my favorite pairings, and adding Remus to the mix is just inspired. Such an excellent character study of him, this quiet, pained man whose life is a constant tale of restraint and denial. I particularly like the way you let your images carry so much meaning: the flowers dripping dew, the subtlety of Minerva's nudging shoulder, the cerulean steam, the carefully-calibrated birthday hug.
Minerva is right that Severus's jealousy is unattractive, but one understands his feelings: both Remus and Minerva are so appealing here that no wonder he fears losing her! Also, I like the way you hint at -- but never answer -- the question of what Minerva's needs are. We see what Remus and Severus might need from her, and I'm now enjoying speculating about what it is she might get from them.
This is not a hint for a sequel. Oh, definitely not. (Just like Remus isn't sill in love with Minerva /g/)