It had always been there-- that jolt of attraction. They'd feel the electricity between them spark and sizzle when ever the other was near, or sometimes, even at the mere mention of a name. The fires were stroked daily by tickle fights and innocent embraces, and soon enough they learned to live with the sensation of their bellies falling to their feet.
James loved Lily; there was never a doubt of that. His heart and soul, every particle of his being went to her. But sometimes, when he'd curl up to his best friend, and those stormy grey eyes would stare at him with the most beautiful expression he'd ever seen. At these moments he'd feel something burst deep in his chest and rush forth, demanding to be released. But he reined it in every time. He loved Lily, and while he loved Sirius in his own unique way, Lily was his future, and both knew it. Sirius brought something new out of James, something great and terrifying, not to mention amazing. After all, Sirius had embedded himself in James' heart and refused to budge--not that the bespectacled boy minded.
Lily could see it all, of course. She wasn't the brightest witch of her age for nothing. She tried to accept it as a fact of life-- they were best friends, and they had to love each other. But it hurt her to find them wrapped into each other, James' glasses left to the side, leaving his face soft and unfocused. He'd stare up at his friend adoringly, while Sirius, well, the look in his eyes always took her breath away. He never looked at anyone else this way; no other conquest earned the look James always received. It was a gaze filled with love. Not teenage lust or infatuation, but pure, unalterable love. There was no bravado, no pretense, just his raw feelings, beaming from his eyes, into James. Who, fortunately, was half-blind from his lack of glasses. Every time she saw it, she'd cry until she fell asleep.
On Lily and James' wedding day, Sirius was all smiles and loud, obnoxious laughter. No one could see his world crumbling, nor his heart breaking. He was the best man, he held the rings. He helped bind the man he loved more than life itself to a woman, he both loved and respected, but for very different reasons. After the wedding he bid the happy couple goodbye, and then stood in the road until their brooms were out of sight. He continued to stand there, silent tears coursing down his cheeks and he said goodbye to his heart, and hello to the aching void it left.
After several years of living with this void, he became dark and withdrawn. He loved his godson immensely, but he couldn't stand to be near his parents for extended periods of time. It seemed that James had forgotten the love they had shared. He doted upon Lily and Harry as if they were royalty, and it threw Sirius further into his gloom. The night the Potters were killed, Sirius was out, drinking himself into oblivion, thinking about what could have been if he'd shown his love in more than just his eyes. He then flew, drunkenly to their demolished house, pulled his godson from the rubble and wept. After the "death" of Peter Pettigrew, it was easy to believe Sirius a spy. He was manic, so crazed in his need for revenge that all who saw him, saw the black-hearted murder they wanted to see. Only the dementors, in the darkest parts of the night saw his true demons. And they played them over and over in front of listless, half-dead eyes;
James curled into his lap, smiling up at him, then morphing into his cold corpse while Sirius wept over the child he'd never get to see grow.