WASHINGTON — Three relatives of Americans who the authorities said were killed by immigrants living in the United States illegally will attend President Trump’s first address to Congress on Tuesday, signaling his plans to showcase his administration’s early efforts to crack down on immigration as a security issue.

Jamiel Shaw Sr., whose son was shot and killed in 2008 by an undocumented immigrant, will also be among the six guests invited to sit with the first lady, Melania Trump, during the speech. Mr. Shaw became one of the most vocal advocates of Mr. Trump’s tough stance on immigration during his presidential run, appearing in a television ad on his behalf and giving a prime-time speech at the Republican National Convention.

Mrs. Trump will be joined by Jessica Davis and Susan Oliver, the widows of two California law enforcement officers who, officials have said, were shot and killed in 2014 by a Mexican immigrant who was in the country illegally. The officers were Michael Davis Jr. and Danny Oliver.