Sirius has never been in love. He's loved people and things and places but he's never been in love. At school he was young and adventurous and rebellious and there were so many better things to be doing and who wants a girlfriend anyway? And then he was still young and adventurous and rebellious and there was a goddamn war to fight and he didn't have time for shit like that and he didn't want it anyway because he was going to be a swinging bachelor for life and his friends would all get married with kids and he'd be best man and god father but settling down was nothing he ever wanted no matter how much everyone thought this was a phase he'd grow out of.
Then his life ended on October 31st, 1981 and dead people can't fall in love and even if they could, he's a mass murdering lunatic and no one's exactly interested. And then there's breaking out and running for his life and dedicating all his love to loving a boy that looks so much like James he feels like his heart is swelling and breaking every time he looks at him. And then he's dead in body and his spirit stops being dead when James gives him that stupid ass grin and it doesn't matter that he's never been in love because he fucking loves James fucking Potter more than anything else and anyone he ever fell in love with would just be jealous anyway.