Hernandez, who turns 21 Tuesday, rushed to the side of Giffords, D-Ariz., and immediately gave her first aid after she was shot in the head outside a supermarket Jan. 8 in a rampage that left six dead and 13 injured.
At a nationally televised memorial service in Tucson Jan. 12, President Barack Obama called Hernandez a hero, even though Hernandez said he didn't consider himself one.
Also attending Tuesday night's address as guests of the first lady will be the family of 9-year-old Christina Taylor Green, the youngest of those killed in the Tucson assault, Gibbs said. Green was born Sept. 11, 2001.
Other guests will include U.S. Army Staff Sgt. Salvatore Giunta of Hiawatha, Iowa, the first living service member since the Vietnam era to receive the U.S. government's highest military decoration, the Medal of Honor, and Brandon Fisher of Berlin, Pa., whose small business made drill bits and other equipment that helped rescue 33 miners trapped in a Chilean mine.
All the guests will sit in the first lady's box overlooking the House floor.
At least two U.S. Supreme Court justices -- Samuel Alito, nominated by President George W. Bush, and Antonin Scalia, nominated by President Ronald Reagan -- said they did not plan to attend the address.
Scalia told The Hill Monday he hadn't "gone to the State of the Union in at least 10 years, and I'm not starting tomorrow night either."
At last year's State of the Union speech, with six Supreme Court justices in attendance, Obama denounced a recent campaign-finance ruling, saying it reversed 100 years of precedent and would "open the floodgates" for corporate spending on elections. Alito shook his head and mouthed "not true."
U.S. Rep. Joe Wilson, R-S.C., who yelled out "you lie" Sept. 9, 2009, while Obama addressed a joint session of Congress to outline his healthcare-reform proposal, said Monday he would join nearly 70 Democrats and Republicans who agreed to sit side by side in the House chamber this year, rather than in their traditional partisan seating arrangements.
"Honored to be sitting besides two fellow HASC members at tomorrow night's SOTU, Susan Davis (CA-53) and Madeleine Bordallo of Guam," Wilson wrote on the Twitter microblogging service.
Davis represents California's 53rd Congressional District, including parts of San Diego. Both she and Bordallo are Democratic members of the House Armed Services Committee.
After the Tucson shootings, U.S. Sen. Mark Udall, D-Colo., proposed the seating changes to demonstrate a sense of oneness on Capitol Hill.
"Partisan seating arrangements at State of the Union addresses serve to symbolize division instead of the common challenges we face in securing a strong future for the United States," Udall's letter proposing the idea said.