An inconspicuous essay about war veterans published in the pages of North Korea’s party-run newspaper on Wednesday appeared to differ little from Pyongyang’s standard propaganda, praising Kim Jong Un’s leadership and expressing hope that his descendants will forever remain loyal to the ruling party.

But the byline affixed at the end revealed a surprise: The author is a North Korean professor who reunited with his long-lost siblings in Seoul a quarter century ago, and who had not been heard of for over a decade.

The essay, titled “An Aging War Veteran, I Will Be Faithful to the Call to the