When he'd met Hisana and was smitten with her, he had taken her in and ignored the complaints that ricocheted behind his back -but within hearing distance, sadistically enough- about the inappropriateness of their relationship. They'd gotten married, and he was content with the idea of her getting to know him, and hopefully love him over the years. He could feel himself changing for the better. Compassion grew, and more than the meager share of tolerance he'd had before flourished, but with her death, reality gave him, yet again, one of it's harsh blows.
He hadn't really lived since then, but searched for Hisana's sister like she had asked him to while he was hovering beside her death bed. When he'd found her, just as small as Hisana but bursting with life and potential, he gave a sigh of relief and immediately fulfilled his promise. He had been ready to try and change again, but she stayed cool to him, always proper, and he could never find the right moment to open himself to her, to show that he was willing to have the close relationship he assumed brothers and sisters had. So, when she was accepted into the Gotei-13, he handed her over to Ukitake and his fukutaichou, Shiba Kaien.
He saw Rukia blossom into what he had always know she could be and it quelled the pain of disappointment at his failure at relationships. Seeing change always makes you crave it yourself, and it slowly crept into him. Just when he thought he could nurture his hope, the hollow came. Kaien died. And Rukia drew further into herself -and away from him- than ever before. That was when he had killed his hope.
When Abarai Renji transferred over from the 11th squad, all whoops, hollers, and uncouthness, he'd been secretly amused. Even if he couldn't see it in himself, the potential in others always lit up the flames inside him. The long thought dead embers of hope rekindled themselves. Sure, he had to sand over the rough edges and get Renji to restrain himself at least a little, but the luminous glow of youth and power shone from him. It made Byakuya wonder when he started to think of himself as not-young. Not even in his mind would he dare say 'old'.
Then, the douse of cold water drenched his life again. The two promises he made, both somewhat contradictory to each other in the first place, clashed violently as Rukia was sentenced to death. Feeling his own pain and sensing it in his fukutaichou didn't knock the kind of sense into him that it did in other people. That kind of sense was forcibly inserted via one Kurosaki Ichigo.
That walking fire of justice -the kind Byakuya had once believed in- sparked his own. Looking back, he secretly wished it had happened sooner, that he had never strayed so far from himself to ruthlessly slaughter his own fukutaichou, turn his back, and leave him for dead. Doing something like that, no matter the reason, made him disgusted with himself. Renji's forgiving, or rather, 'Hey. We both had to do what we had to do.' attitude only soothed him slightly. It was the return of the light in Rukia's eye, her boisterousness and laughter, that really saved him from a kind of self-imposed despair.
So, Kuchiki Byakuya began to heal, and just like Hisana, Rukia, Kaien, and Renji before him, Ichigo once again started the seed of hope and change growing. This time, Byakuya thought to himself, he would nurture it and not let reality crush it like the times before. It was time for a fresh start.