When the pope was chosen, two tailors were ready in Rome.

But Cardinal Robert Francis Prevost, who prepared for the conclave, took it off when his older brother called from Illinois.

“He said,” Really not, not going to happen, “recalled Mr. Prevost, 71, who retired from a career as an educator and school director.

Of course it happened. Cardinal Prevost is now Pope Leo XIV, the first American pope. And for his friends and family back in Illinois, where the pope grew up, everything is different.

In a wide interview on Thursday afternoon in his house in New Lenox, a tidy city of 27,000 people about 40 miles southwest of the center of Chicago, John Prevost thought about the climb of his brother to the papacy, the values ​​of the new Pope and his American roots.

Leo, who is used to call the Lord Prevost Rob, “has a great, great desire to help the oppressed and the detached, the people who are ignored,” said Mr. Prevost. He predicted that his brother would continue the legacy of his predecessor, Pope Francis.

“The best way I could describe him now is that he will follow in the footsteps of Francis,” said Mr. Prevost. “They were very good friends. They knew each other before he was Pope before my brother was even Bishop.”

Mr. Prevost said that he usually spoke with his brother by telephone every night, but had not spoken to him since the conclave started. He said that the new pope was “simple, really. He doesn’t go out for a meal of 19 courses.” Last August, Mr. Prevost said, his brother stayed at his home in New Lenox for a few weeks.

The brothers grew up in Dolton, Illinois, just outside Chicago, and went to church and school in St. Mary of the Assumption Parish on the south side of Chicago. Their father, Louis Prevost, was a school inspector and their mother, Mildred Prevost, was a librarian who was deeply involved in parish life. In addition to John and Robert, now Leo, the Prevosts had another son, who now lives in Florida.

The future Pope left Illinois to go to high school in Michigan and the University in Pennsylvania, but returned to his home for the Graduate School and for various reports with the Augustinians, the religious order he was a member of. Leo also spent a large part of his career in Peru.

John Prevost described Pope Leo as “in the middle of the road” and said, “I don’t think we’ll see extremes anyway.” But, he said, his brother would not be afraid to use this new platform.

“I don’t think he will stay quiet for too long if he has something to say,” said Mr. Prevost. “I know that he is not happy with what is going on with immigration. I know for sure. How far he goes with it is just a gamble, but he won’t just lean back. I don’t think he will be the quiet.”

When asked if his brother had expressed the wish to be pope, Mr. Prevost said “not really.” But over time, while he rose the ranks of the church, his answer to that question began to shift.

“It was” absolutely not, absolutely not, forbid God, “said the Lord Prevost.” And then it became, “Well, if it is what God wants, then we will deal with it.”

Thursday was a blur for Mr. Prevost, whose telephone constantly called during an interview and whose street was held with news trucks.

“I understand that people are interested because it is a scoop in so many ways,” said Mr. Prevost.

Asked what his parents, who died years ago, would think, he said, “They would be on cloud 9. Absolutely incredible. You couldn’t even dream this.”

When he is finally able to reach his brother, Mr. Prevost said that he was planning to ask what he would do for relaxation and whether he would ever really be out of work. He said he hoped to see him in Rome, but did not know how that would work yet.

In the immediate term, however, there was one important fact to clean up. The pope, Mr. Prevost said, was not a fan of the Chicago Cubs, as some had reported. He had always welcomed the White Sox.