Dong-joo, with the help of his father, had attempted to oust his younger brother from Lotte Holdings, the conglomerate's Tokyo-based holding firm, while Dong-bin has countered by demoting their 93-year-old father from key posts, implying that the founder's old age has blurred his mental capacity.

"My father, the general chairman, gave me the full authority to sue Shin Dong-bin and other executives at Lotte Holdings," the elder brother said in a statement. "The general chairman is very distressed and wants to punish my younger brother and related people."

In August, Shin Dong-bin bagged a landslide win at a hastily arranged shareholders meeting of Lotte Holdings, ending the family squabble. But his elder brother's countermeasures heralded a twist in their power struggle.

The family feud, meanwhile, has expanded into one of the country's biggest family fights of all time, previously seen among scions of the country's chaebol, such as Hyundai and Kumho.

Anti-chaebol sentiment has also been building up, which for Lotte translates into a possible boycott of its services and products by consumers, a substantial threat for the heavily retail-focused company.

In efforts to reduce public backlash, the Lotte chairman has pledged to simplify the group's ownership structure and enhance corporate transparency. Separately, the group has also announced plans to hire more workers in support of the government's drive to boost employment. (Yonhap)