Schreyer added that the two marques would always share mechanical hardware "because it makes sense to do so", but there is scope for unique models within each marque to be further developed as sub-brands in the future.
"There are cars out there that are a kind of sub-brand, like the Golf for Volkswagen, which is a brand in itself, [and it is the same with] Genesis for Hyundai and the Soul for Kia," he said.
But the ex-Audi stylist who has helped turn Kia's designs around since 2006, ruled out any stand-alone luxury brand developments for either company in the Lexus/Infiniti/Acura mould, for the near future at least.
"In one way, to create a new brand could be a charming idea," Schreyer admitted.
"But on the other hand, if those cars that would be in that segment were to be called Hyundais it would make the brand stronger.
"If you separate the cars too much and they are not recognisable, and then you have to spend billions in advertising and making that brand.
"If you look at Lexus it took over 20 years for them to get where they are, but at the same time image-wise it did not pull Toyota up at all because it is a Lexus.
"So this is why in our case it is best not to do it."
Asked how he would describe Kia and Hyundai's styling against each other right now, Schreyer describes the former's as a snowflake compared with the latter's raindrop.
"Kia has created an identity and extended our product range with nice concept cars where one might see the light of day," he said. "We have established a very distinctive body language while Hyundai has done some spectacular designs that have been very successful. I would say the differences are like that of the snow crystal and raindrop, with Kia being the snow crystal.
"Hyundai's design has been quite daring and spectacular. They've created their own direction that did not look like it has been copied from somebody else," Schreyer said.
"But I think some of Hyundai's design has been exaggerated, and a little bit over the top, and it needs to be refined - but I would not make a 180-degree turn and say, 'No, you do something completely different now.'
"There is now a nice difference between the way Hyundai and Kia are perceived.
"Kia is more youthful, more of the challenger, fresher and somehow still perceived as a new brand, while Hyundai is more about elegance - and without the negative connotation - more on the classic side," Schreyer explained.
"There is a substance there on both sides, and we can't throw everything that we've previously worked on away."
