In Chicago, a city where baseball allegiance has no middle ground, one of the first questions people asked was whether the Chicago-born pope cheered for the White Sox or the Cubs.

The lines dividing Cubs and Sox fans are not always clear. Generally speaking, North Siders root for the Cubs, since Wrigley Field is on their side of the city. South Siders are usually loyal to the Sox, who play at Rate Field in Bridgeport, on the South Side. Suburbanites tend to follow the same geographical divisions, but are sometimes considered a gray area.

Fans from both sides seemed to initially claim the new pope as their own. A spokeswoman for the Cubs first said that she could not confirm whether he was a fan, and issued a statement from Tom Ricketts, the executive chairman of the Cubs, assuring the new pope that he would be welcomed at Wrigley Field.

“Not only would we welcome Pope Leo XIV to Wrigley Field, he could sing ‘Take Me Out to the Ball Game’ or, since three of his predecessors visited Yankee Stadium, including Pope Paul VI who delivered the 1965 ‘Sermon on the Mound,’ we would invite the pontiff to do the same at the Friendly Confines,” Mr. Ricketts said.

By afternoon, the marquee at Wrigley Field declared that the new pope was a Cubs fan.

But in suburban Chicago, the pope’s brother John Prevost set the record straight to WGN, a television station that for decades broadcast Cubs games and helped create a fan base far beyond Chicago.

“He was never, ever a Cubs fan,” Mr. Prevost said. “So I don’t know where that came from. He was always a Sox fan.”