stefan salvatore,  born as stefano antonio salvatore, was born in 1490 in florence, italy to an aristocratic, noble italian family : conti di giuseppe salvatore and contessa di salvatore. little is known about the woman that birthed him as she passed away a few years after giving birth to stefan. after the passing of the contessa, the salvatore brothers endured terrible abuse at the hands of giuseppe, who had since turned to alcohol. 

when damon went to university, stefan attempted to get closer to giuseppe in hopes of making his home life more tolerable, but his attempts were in vain, and would often end in violence. stefan's childhood was scarred from a young age, and he carries the trauma, the guilt, the remorse to this day which makes him an introverted, reserved, quiet person. 

during the summer of 1508, baron von swartzschild, a german nobleman and a friend of giuseppe, came to italy from germany with his young daughter katerina and stayed in the salvatore estate to help katerina with her recovery from a dreadful illness, which had severely weakened her already fragile state. over time, stefan fell in love with katerina, who later revealed to him that her illness was, in fact, vampirism.

upon getting over the initial shock, over the following months, stefan and katerina spent a lot of time together and their fathers had even began discussing the prospects of possible marriage between the two. damon's sudden return from university would be what would put a halt to such plans. damon's attempts of turning katerina and her attention, affection into a competition between them made stefan jealous, unhappy and lead him to ask her to choose between the two of them whomst she would like to marry. 

katerina tricked the brothers by sharing her blood with the pair of them, wanting them to be together forever. the brothers were given lapis lazuli silver rings which would help to protect them from the sunlight after they completed their transitions into vampires. neither could accept this and argued that she must choose between them and that they would never be fine with sharing her. 

later, the brothers searched for katerina but couldn't find her. stefan then remembered that her favorite place to hang out was under the lemon tree, and he stumbled across katerina's dress covered in smelly ash, with her 'daylight ring' on a rock with a note, saying she had committed suicide in the hopes that the brothers would end their rivalry, reconcile and love each other again. 

this event ended up in a sword-fight. damon managed to get under stefan's guard and stabbed him right through the heart, killing him almost instantly, and stefan retaliated with every bit of strength left to stab damon in the heart too, killing him. with katerina's blood flowing within their bloodstreams, they both began their transition into vampires.