It didn't take long after Cardinal Robert Prevost, a Chicago native, was chosen as the new pope for social media to catch fire with the most Chicago of debates: Is Pope Leo XIV a Cubs fan or a White Sox fan?
The Cubs shared a post on X showing a new message on the iconic Wrigley Field marquee that declared, "Hey, Chicago, He's a Cubs fan!"
But the new pontiff's brother, John Prevost, said his younger brother has been a proud White Sox fan since they were altar boys growing up in Dolton.
"They had it wrong. He's Sox, and then the radio announced Cubs, and that's not true," John Prevost told CBS News Chicago, adding that the new pope has been a White Sox fan "as long as I've known him."
The Prevost brothers frequently attended White Sox games growing up.
"Yes, we did. Because really, from Dolton to Sox Park wasn't that big of a deal, and of course we were both altar boys, so that was one of the rewards that we got was to go to a Sox game," John said.
In a statement, the White Sox said, "Family always knows best, and it sounds like Pope Leo XIV's lifelong fandom falls a little closer to 35th and Shields."
"Some things are bigger than baseball, and in this case, we're glad to have a White Sox fan represented at the Vatican. A pinstripes White Sox jersey with his name on it and a hat already are on the way to Rome, and of course, the Pontiff always is welcome at his ballpark," the team added.
After learning the pope's brother had settled the debate, the White Sox were quick to share the news on the scoreboard at Rate Field, mocking their North Side counterparts: "Hey Chicago, He's a Sox fan!"
Leo has two older brothers, John and Louis, who have been there for his journey from altar boy to the papacy.
John, a retired Catholic school principal, said the brothers had a normal childhood and traditional Catholic upbringing. They were all altar boys, but Leo knew from a young age he wanted to be a priest.
"You know how some kids like to play war, and be soldiers, and some girls want to play dolls, and be housewives? He wanted to play priest, and so he took our mom's ironing board, and put a tablecloth over it, and we had to go to mass," John said. "We went to mass, and he knew everything. He knew the prayers in Latin, he knew his prayers in English, and he did that all the time. He took it totally serious. It was not a joke, it was not a game. He was dead serious about it. Isn't that interesting?"
John said one of the mothers on their street told Leo in kindergarten or first grade that he would become the first U.S.-born pope. John said he is confident his brother will be a great pope because he didn't seek the papacy.
"I think the very fact that in his heart and in his very soul, he wanted to be a missionary. He didn't want the bishop, he didn't want the cardinal, but that's what he's asked to do," he said. "I think you'll see a second Pope Francis. I think. And then he'll take some things on himself. He's young to be a pope, I think, and he's active. So he will be here and there, and moving around, and I think he will also speak his mind."
What comes to mind when he now hears the name Pope Leo XIV when people talk about his brother?
"Shock. Disbelief. A whole lot of pride. A whole lot of, is this for real? Now what are we going to do? That kind of stuff, because this is an awesome responsibility that we have to live up to, that he has to live up to. People are going to be watching him from now on, closer than ever, and maybe us too, the family," he said.
John said he hasn't had a chance to speak to his younger brother since he became pope, but he is headed to Rome on Friday to be part of the celebrations at the Vatican.
More from CBS News
Dorothy Tucker