Kiyoko Kimura was born into a rich family in Ba Sing Se. The direct members of the Kimura family were all non-benders, so a long story short, earning a worthy status and wealth took a lot work, but the family had made it eventually. Kiyoko is the third child of five children, as well as the only girl born into the Kimura line.
She spent her life living with her siblings in the estate, rarely able to see her mother or father as they were always deeply focused on their business. Residing with four brothers meant one thing in her case: she was easily toughened up, influenced to be a tomboy. Gender and size meant nothing, as she grew up a stubborn, brave, brash, blunt and almost bitchy little brat- I mean, kid. She often joined her brothers in rough games or even wrestling. Wrestling in which she took pride in winning over half the time.
The week after her 7th birthday, she shocked every member of her family by showing obvious signs of earthbending. Her father, after overcoming shock, was quite delighted. He concluded that she may have inherited the ability from her late great aunt- as she was the only one her father knew of possessing the same bending. Eventually her mother came to delight with too, obvious by the bright smile she gave her young daughter. Her brothers admitted they were jealous, but they were intimidated to confront her about it.
Her father got quality teachers to train her skills, but Kiyoko always felt like doing it her own way, so it constantly strains her relationship with each bending teacher her father hires. Her parents had forgotten about it apparently, they didn't give her a second glance ever since finding out about her earthbending. So she started showing off her ability in order to gain at least a glance from them, but alas, no more than ticking offs and disapproval. But as stubborn as she was, she ignored her sad feelings and kept trying to win her parents' attention.
Over the years she came to terms with giving up and learning the showing off and acts were pathetic and useless. Thus this caused her to be ill-thinking and not giving her parents the time of day when she reached adolescence, more accurately from the age 14. Her older brothers had already gone off working in other fields, leaving her with two younger siblings, but of whom had begun learning the history of their family's company and thus apprentices of their father. Which left Kiyoko alone, with her earth bending and bitter feelings that developed through the dejected years.
Of course one day, unfortunately it had to be after her 21st birthday, without her knowledge or permission, her parents had planned to marry her off to the son of a business man. When Kiyoko found out she was furious, leading to an argument with her parents. Tired, very tired and angry afterwards, she told her parents the marriage was off and left the estate, not before taking enough money and necessities along. She was now a 21-year-old, independent and very sure that she needed fresh air instead of the suffocating heat of being in the estate. Or to not be taken away from her freedom. So she left Ba Sing Se for the Republic City. Never does she want to hear from her family again or go back to the estate.