EXCLUSIVE

The San Diego Chargers will honor the memory of fallen NFL superstar Junior Seau during their home opener on Sunday Sept. 16 ... and TMZ has learned his entire family will be on hand to witness the ceremony.

A rep for the Chargers tells us ... Junior's mother, father, ex-wife, 4 children and other family members will be the guests of honor during a pre-game ceremony dedicated to Seau ... the greatest Chargers linebacker of all-time.

We're told the team will officially retire Junior's #55 jersey during the ceremony ... and the family will be presented with a special "surprise gift" from the organization.

The team will also debut the special #55 helmet sticker, which each Chargers player will wear during the game.

As we previously reported, Junior Seau was found dead in his San Diego home on May 2nd from a self-inflicted gunshot wound to the chest.