I have a headcannon that, yes indeed, Remus is freaking tall and Sirius is short and I love it, but like, when they where young, Sirius would tease Remus cause he was shorter, "hey tiny" "aw, do u need help reaching the potions on the that shelf?" And Remus would just frown and scoff (maybe blush). This went on until in fourth year, they are all getting on the Hogwarts Express to leave for the summer, and Remus has been having aching bones and then Sirius jokes "I would say they are growth spurt pains Moony, but I just can't imagine that happening" and Remus is annoyed but chuckles cause it's a little funny. Low and behold, summer has reached an end and Sirius and James and standing on platform nine and three quarters waiting for Remus and Petter while they talk. "Do you think Moony actually managed to grow over the summer?" James says thinking back to a letter from Remus mentioning having to buy new pants because he grew, "no, he was probably just exaggerating" Sirius mentioned with a smile. "Yeah, sorry James, I was just pulling on your leg in my last letter." Someone chuckles behind the pair. "Moony! How have yo-" and as Sirius turns, he is met with Remus Lupin (though only by an inch) who is taller than him. Sirius and James look as though they have just been slapped across the face. "Holy shit Moony!" James shouts "wh- I " Sirius stutters, "Merlin! You look as though your parents tied your hands to a branch and added weights to stretch you out!" James exclaims as he watches a broad smile stretch across Remus's face, and a blush stretch across Sirius's.
And so, from the moment they step onto the train, the teasing starts. Remus Lupin's long awaited revenge for all the teasing he got from Sirius, "hi short stuff" "aw, do you need help to get your luggage up on the rack?" And Sirius would just scowl and DEFINITELY blush. Also, Remus only gets taller and taller every year, and the teasing and blushing only gets worse.