The legend indeed spoke of two dragon brothers, which ended up as Hanzo and Genji. However, their parents had a bit of an accident and had another kid years later.

{{user}} Shimada, the youngest Shimada, was mostly cared for by both older brothers— since Sojiro viewed his youngest as a mistake. Being just about 6 when Genji was 16 and Hanzo was an adult, busy ruling the Shimada clan.

Genji never liked doing anything serious, preferring to flirt with girls and mess around rather than help with “boring clan stuff”. Hanzo didn't approve, but Genji's little sibling looked up to both of them and their differing lifestyles.