james and sirius were soulmates. they completed each other. yes, james loved lily and sirius loved remus, but james and sirius loved each other utterly and unconditionally.
in first year, sirius received scathing letters from his mother (they dwindled as the years went on, until they stopped, which was worse). his slytherin cousins spat on him and pushed at him and cornered him and ridiculed him. sirius cried a lot that year. james took to going with sirius everywhere, waking up with him in the dorm room and walking to classes with him and sneaking down to the kitchen with him. he was scared for sirius and he protected him.
in third year, sirius stayed back christmas break because he couldn’t deal with his mother. to make matter worse, james had to go back home (it was his grandfather’s funeral). sirius spent most of the two weeks lying on his bed and trying not to think about the emptiness usually filled by his best friend and the letter on his bedside table. that is, until a tawny owl tapped on his window and brought a letter from james, which insisted he burn the letter from his mother (i know you can’t stop thinking about it, mate. don’t let her ruin you) and reminded him to go down to breakfast (if you don’t want to sit in the great hall, at least sneak down to the kitchens. you have to eat) and said, “i miss you sirius. stop thinking about your shitty family and write me or remus or pete instead. make sure you prank mcgonagall for me.” he signed it, “your brother and best mate”.
in fifth year, james asked sirius who he liked. (james had liked lily since they were eleven.) sirius blushed and said he didn’t know, that he couldn’t really imagine ever loving someone like that. that sex seemed disgusting to him. and james looked at him funny, told him truthfully that he couldn’t imagine that, but you do you, mate, and i won’t judge you. we’re still married, though, right? and sirius laughed, and when james caught him giving remus close-mouth kisses, he ruffled sirius’ hair and grinned, and said that as long as sirius was happy, he was happy.
in seventh year, sirius was freaking out. the war was in full swing, he was terrified, and he didn’t trust himself. james took his hand, and told him he loved him, and that he was scared too, and they were going to get through it together. that they were brothers. that he had his back. and sirius knew all this, but he could breathe easier now.
just. james and sirius were closer than friends, closer than brothers. they could look at each other and know what the other as thinking, what they were feeling. they would die for each other. they loved each other.