Kia and Hyundai aren't actually the same company, but they're very closely related. Hyundai group (Hyundai automotive's parent company) acquired a significant stake in Kia when they went bankrupt during the Asian financial crisis. In exchange, Kia received significant percentages of many Hyundai group companies, including automotive. They share components and designs, but they're separate companies with their own teams, factories and marketing.
Seems like Hyundai own 33% of Kia, rather than it just being a brand under the same company like Lexus/Toyota. They share some things and compete on others.
It's a lot more complicated than that. They also have some common owners, and Kia owns parts of some Hyundai subsidiaries. Chaebol's are complicated beasts.
Hyundai and Kia were two separate companies that merged in 1998. Genesis is their premium brand, their Lexus equivalent. They claim to differentiate the three brands with: Hyundai: bold, Kia: sporty, Genesis: premium. Your guess is as good as mine what the difference between bold and sporty is.
