Speculation is growing over the possibility of SK Chairman Chey Tae-won’s younger brother Chey Jae-won returning to management to take the helm of the group’s refining and petrochemicals unit SK Innovation, according to industry sources on Monday.

The junior Chey, who served a three-and-half year jail term for embezzlement in 2014, faced employment restrictions for five years.

Chey Jae-won, who holds a bachelor’s degree in physics from Brown and a master’s degree in materials science from Stanford, was deeply involved in SK Group’s burgeoning battery business. It was him who noticed the potential of the electric vehicle business from early on and recommended his older brother to make aggressive investments in the field.

Even though SK Innovation recently split off its battery business into SK On, he is likely to lead the parent company considering his potential position that oversees the group’s sprawling energy business, sources said.

Despite his employment restrictions, the junior Chey has had a presence around the company as he has attended the group’s key battery events in recent years. He was present when his brother met with Hyundai Motor Group Chairman Chung Eui-sun last year at SK Innovation’s battery plant in Seosan, South Chungcheong Province. He also accompanied the SK chairman in his US trip earlier this year to check the group’s investment status there. He also participated in the groundbreaking ceremonies of SK Innovations’ battery plants in Hungary and the US state of Georgia.

Still, some observers predict that the younger Chey might return to SK E&S, the group’s natural gas and hydrogen business unit. SK E&S is the only SK Group affiliate where he has maintained an official post as an unregistered representative.

The incumbent chief executives of SK Innovation and SK E&S are Kim Jun and Choo Hyeong-wook.