Bruce was born to an American neurologist father and a Japanese psychologist mother. This combination gave Bruce quite the interesting childhood. The second he was born his parents decided to make him part of a life-long experiment, well at least until he grew up. His older sister was also part of this experiment with his two younger brothers being the control groups. Lucky them, they ended up having relatively normal lives.
As for Bruce, being part of an experiment had its ups and downs. His father wanted to prove the effectiveness of rewiring neurons at a young age and his mother wanted to see how rigorous learning affected the development of children. To say the least, he became super smart. Not only that, his father began teaching him many things at a very, very young age one of the things that he grew up with in fact and his favourite sport (if you want to call it a sport) chess, which he became a grandmaster at quite the young age. He was also introduced to science, math, and medicine in his early ages. He quite obviously became a doctor, however his hatred for neurology ran deeper than bone marrow.
As for his mother's part of the experiments, she would teach him strange social behaviour as a child - things like being rough, dominant, or alpha-male if you will. She wanted to see if the whole learning and becoming a genius inhibited one from socialising and proving his dominance over other males. To prove this was wrong, she signed him up to a martial arts class where he learned the basics of self-defence at the age of five to ten. From then on, when he saw fencing on TV in the Olympics, he had gained a deep love and joined a fencing team where he practised it well up until his death. Now, the experiment did have it's good sides. His father was very good looking and his mother was exeptionally beautiful, now winning the gene lottery said a lot, but having a sculpted body along with the usual alpha-male attitude and being smarter than the school's genius, it wasn't unusual that he was hit on everyday.
He grew up and went to Cornell University in New York where he got his medical degree then moved to Karakura town, his mother's home town to pursue his manipulated-upon dream of becoming a doctor. He also took various forms of martial arts while in Japan and was quite obviously a formidable foe, for not only was he strong and fast, but he knew the body inside out (perks of being a surgeon) and knew the precise landmarks to strike to render his opponent stunned.
As strange as his life was, and strangely entertaining, it would soon, and sadly have to come to an end in the living world, and a tragedy it is for parents to see their young die before them. He was driving home in his Bugatti Veyron (oh, how he loved his dad!) when a drunk driver, who unfortunately happened to be driving a truck, rammed Bruce's car on the driver's side. The amount of times the Bugatti rolled was unknown but the damage was as if there was a plastic explosive under the car; there was nothing but scraps left. The body of Bruce totally mutilated beyond recognition. He died on the spot.
And thus his life in soul society began.
How long he lived in the outskirts of the Gotei Thirteen he can't recall, but what he can are scraps and pieces of his time there. He was quite obviously poor when he was living in the outskirts, which he really never got used to but had enough discipline in him to accept things as they were. His neighbours would hear him constantly grunting and panting during the nights (I bet they had some ideas) and well into the morning never letting his body get out of shape. It was on one of these faithful days that two shinigamis were patrolling the area Bruce happened to be staying in. However, it wasn't the best of circumstances, not for these shinigami at least.
You see on this day Bruce had been quite angry because he lost a game of chess to himself which he knew he could win. As he was walking and going over and over the game he bumped into a shinigami. Now, let's be honest shinigamis are ass holes and thinking they're all high and mighty they made the dire mistake of shoving Bruce. For one of them, it's the worst mistake he's ever made. Bruce immediately tried to strike the neck of one of the two shinigamis, however being trained in flash-step he was able to dodge the strike. The other, let's call him number 2, pulled out his zanpakuto and tried to bring it down in an arch to eventually go horizontal and through Bruce's neck. He saw the intent clearer than a dandelion in mid-summer's eve held by a dancing cow wearing bling. Also, thanks to his years of training as a kid, he developed a sort of sixth sense where he could somewhat "feel" a person coming at him from the back (perks of being a fighter).
Bruce's strategic mind kicked into overdrive and he visualized what he thought to be all the possible and most effective attack methods with the best possible outcome. Trusting his instincts he jabbed the number 2's right axilla, ducked from an on coming round-house kick from number one, stood up, took a small makeshift blade and stabbed and cut across number 2's right brachial plexus rendering his sword arm completely useless and rolled out of the way of a sword sweep from number 1 as number 2 fell screaming in pain trying to suppress the blood gushing from his neck.
Number 1 enraged that a simpleton somehow felled his companion used kido #9 paralysing Bruce, who was very shocked at the red light that suddenly appeared around his body which made him paralysed. Apparently unaware of his own coming doom the only thing running through his mind was that the stupid shinigami cheated. But then again, shinigamis are ass holes. After number 1 paralysed Bruce he gave him a beating that turned his face into bloody mess of mashed potatoes. It wasn't long after until another shinigami, one whom Bruce thought was a superior came and ordered number 1 off of him. After number one explained what had happened the superior shinigami looked at Bruce in utter astonishment, or so Bruce claims, his eyes were shut from the bruising and he has no substantial proof except for the chocking sounds the superior was making.
He was taken inside the Gotei thirteen's medical ward where he was healed and was instantly admitted into the training academy. Except for the kido and other strange magical stuff, Bruce really has little talent for such things, he was excelling and was almost a genius in the academy (perks of having crazy parents). After he graduated his tactical skills were noted among the best of his group, he was put into the 10th division.