After years in which his privacy has been fiercely guarded and he has been kept out of the political arena, former President Donald J. Trump’s youngest son, Barron, was chosen to be one of Florida’s delegates to the Republican National Convention.

Barron, who turned 18 earlier this year and will graduate high school this month, will be one of 41 at-large delegates at the party’s national meeting in July, when the G.O.P. is expected to officially nominate his father as the Republican presidential candidate. His selection was reported earlier by NBC News.

The youngest Trump will be joined in the delegation by his two more politically active brothers, Eric Trump and Donald Trump Jr., both of whom have appeared on the campaign trail or done interviews to support their father’s candidacy.

Mr. Trump’s younger daughter, Tiffany, will also be a Florida delegate. Ivanka Trump, his eldest child, was not on the list.

Though politicians’ children often hit the trail to stump alongside their parents, Barron Trump has largely been absent from his father’s campaign this year. It remains to be seen whether he will give a speech at the Republican convention, as his siblings did in 2016 and 2020.

For the past several years, Barron has been attending a private high school near Florida. His graduation, on May 17, became a point of contention in Mr. Trump’s hush-money trial in Manhattan because it overlaps with the court schedule.

The judge in the case initially delayed a decision on whether court would be in session that day, prompting complaints from Mr. Trump, but he eventually agreed to allow the day off from court.

The Florida party’s list of delegates further demonstrates the extent to which the Trump family and Mr. Trump’s supporters have moved to the center of Republican politics. His daughter-in-law, Lara, who is married to Eric Trump, was made co-chair of the Republican National Committee earlier this year.

The Florida delegation list also includes Kimberly Guilfoyle, the fiancée of Donald Trump Jr., and Michael Boulos, Tiffany Trump’s husband. Other longtime Trump allies were also chosen, including Isaac Perlmutter, the former Marvel Entertainment chief executive who is a major donor, and the real-estate investor Steve Witkoff, a longtime friend of Mr. Trump.

Michael C. Bender and Patricia Mazzei contributed reporting.