Destined to be pope: Brother says Pope Leo XIV always wanted to be a priest

When Cardinal Robert Prevost was in the first grade, his neighbor told him he would be the first American pope, his brother told ABC News.

On Thursday, that prophecy came true, when Prevost was elected to be the 267th pontiff, the first from the United States.

Before he was Pope Leo XIV, the 69-year-old pontiff grew up the youngest of three brothers in the South Chicago suburb of Dolton.

He always wanted to be a priest, his middle brother, John Prevost, told ABC News.

"He knew right away. I don't think he's ever questioned it. I don't think he's ever thought of anything else," John Prevost said.

As a child, Pope Leo XIV "played priest," John Prevost said. "The ironing board was the altar."

Pope Leo started to emerge as a front-runner for the papacy in the days before the conclave began, according to the Rev. James Martin, a papal contributor to ABC News.

John Prevost said he spoke to his brother on Tuesday, before the cardinals went into the secretive conclave, and told his brother that he also believed he could be the first American pope. Pope Leo called it "nonsense," saying, "'They're not going to pick an American pope," his brother said.

"He just didn't believe it, or didn't want to believe it," John Prevost said.

As the new pope, John Prevost said he expects his brother will follow in the late Pope Francis' footsteps as a voice for the disenfranchised and poor.

"I think they were two of a kind," John Prevost said. "I think because they both were in South America at the same time -- in Peru and in Argentina -- they had the same experiences in working with missions and working with the downtrodden. So I think that's the experience that they're both coming from."

His oldest brother, Louis Prevost, told Sarasota ABC affiliate WWSB that he was "half expecting it, half not," adding, "I still was in shock." Louis Prevost said he was feeling under the weather and lying in bed at the time the big moment came.

"My wife called and said, 'white smoke, white smoke,'"Louis Prevost told WWSB. "So I turned the TV on, watched the white smoke. It took almost an hour till [the elected pope emerged from St. Peter's Basilica] and when the cardinal came out, and we're all waiting, and he goes, and he mentioned Roberto, I knew right away."