The wrongful death lawsuit, filed Wednesday in California Superior Court in San Diego, blames the NFL for its "acts or omissions" that hid the dangers of repetitive blows to the head. It says Seau developed chronic traumatic encephalopathy (CTE) from those hits, and accuses the NFL of deliberately ignoring and concealing evidence of the risks associated with traumatic brain injuries.
"While Junior always expected to have aches and pains from his playing days, none of us ever fathomed that he would suffer a debilitating brain disease that would cause him to leave us too soon," his family wrote in a statement.
Seau died at age 43 of a self-inflicted gunshot in May. He was diagnosed with CTE, based on posthumous tests, earlier this month.
"For sixteen years, the NFL actively and continously denied any link between MTBI sustained by former NFL players in NFL games," the lawsuit claims.
The family added that while they know the lawsuit won't bring Junior back, "it will send a message that the NFL needs to care for its former players, acknowledge its decades of deception on the issue of head injuries adn player safety, and make the game safer for future generations."
An Associated Press review in November found that more than 3,800 players have sued the NFL over head injuries in at least 175 cases as the concussion issue has gained attention in recent years. More than 100 of the concussion lawsuits have been brought together before U.S. District Judge Anita B. Brody in Philadelphia.
Helmet manufacturer Riddell Inc., also is being sued by the Seaus, who say Riddell was "negligent in their design, testing, assembly, manufacture, marketing, and engineering of the helmets" used by NFL players. The suit says the helmets were unreasonably dangerous and unsafe.
"Players did not know the long-term effects of concussions and relied on the NFL and Riddle to protect them," the lawsuit claims.
Seau was one of the best linebackers during his 20 seasons in the NFL. He retired in 2009.
Click here to read more about Junior Seau
Plaintiffs are listed as Gina Seau, Junior's ex-wife; Junior's children Tyler, Sydney, Jake and Hunter, and Bette Hoffman, trustee of Seau's estate.
The lawsuit accuses the league of glorifying the violence in pro football, and creating the impression that delivering big hits "is a badge of courage which does not seriously threaten one's health."
It singles out NFL Films and some of its videos for promoting the brutality of the game.
"In 1993's 'NFL Rocks,' Junior Seau offered his opinion on the measure of a punishing hit: `If I can feel some dizziness, I know that guy is feeling double (that)," the suit says. "By returning to games while he was still suffering the symptom of subconcussions or concussions, Junior Seay was exposed to the risk of greater trauma to his brain."
The NFL consistently has denied allegations similar to those in the lawsuit.
"The NFL, both directly and in partnership with the NIH, Centers for Disease Control and other leading organizations, is committed to supporting a wide range of independent medical and scientific research that will both address CTE and promote the long-term health and safety of athletes at all levels," the league told the AP after it was revealed Seau had CTE.
The lawsuit claims money was behind the NFL's actions.
"The NFL knew or suspected that any rule changes that sought to recognize that link (to brain disease) and the health risk to NFL players would impose an economic cost that would significantly and adversely change the profit margins enjoyed by the NFL and its teams," the Seaus said in the suit.
The National Institutes of Health, based in Bethesda, Md., studied three unidentified brains, one of which was Seau's, and said the findings on Seau were similar to autopsies of people "with exposure to repetitive head injuries."
"It was important to us to get to the bottom of this, the truth," Gina Seau told the AP then. "And now that it has been conclusively determined from every expert that he had obviously had CTE, we just hope it is taken more seriously. You can't deny it exists, and it is hard to deny there is a link between head trauma and CTE. There's such strong evidence correlating head trauma and collisions and CTE."
In the final years of his life, Seau went through wild behavior swings, according to Gina and to 23-year-old son, Tyler. There also were signs of irrationality, forgetfulness, insomnia and depression.
"He emotionally detached himself and would kind of 'go away' for a little bit," Tyler Seau said. "And then the depression and things like that. It started to progressively get worse."