It has been an inauspicious return to crisis-plagued South Korea for former U.N. chief Ban Ki-moon, once the odds-on favorite to be the next president, who has been ensnared in a family corruption scandal and struggled with a skeptical press.

Ban, 72, has been unable to capitalize on his much-anticipated homecoming after a decade as secretary-general of the United Nations in New York. Since his return on Jan. 12, he has cut a sometimes-irritable figure in public and been pilloried for a series of perceived PR gaffes — all without announcing any intention to run for president.

Now the United States has asked South Korea to arrest his brother, Ban Ki-sang, on charges that he engaged in a bribery scheme to carry out the sale of a Vietnamese building complex.