Henry King Jr. was likely born within 2-3 years before or after 1960, the son of mutant criminal and megalamonic Henry (Brain Wave) Sr. and former teen age adventurer Merry (Girl of 1,000 Gimmicks) Pemberton King. The circumstances of his parents meeting and marriage and his earliest days are largely unrevealed.  It is known that he was kept largely ignorant of his parents famous lives as a child and whatever the elder King's failings, he was loved by his son whose relationship with was complicated.

Henry King Jr. first came to the public attention in 1984 when he barged into a meeting of the Justice Society in the aftermath of the encounter with their children and god-children, the future Infinity Inc.  The JSA battled King who appeared as his father but the battle was inconclusive as King escaped (Infinity Inc. #1-2).  From there, he followed the young heroes into the past to confront the Ultra-Humanite and his Secret Society of Super-Villains, including his father, the original Brain Wave.  Defeating the Ultra-Humanite in 1942 sent his father back to Limbo and the young heroes back to the 1980's (All-Star Squadron #24-26, Annual #2).

Back in the normal time, the young heroes formed their own second generation team under the leadership of the Star-Spangled Kid known as Infinity Inc and moved to Los Angeles.  King became a member using the moniker Brainwave Jr. Shortly thereafter, the were again besieged by the Ultra-Humanite, the current one  this time.  He had used the waters of Koehaha, the Stream of Ruthlessness is Colorado to convert several JSA members into criminals.  As the deranged heroes battled the Infinitors, Brain Wave Jr and Star-Spangled Kid confronted  the mastermind himself.  As the Ultra-Humanite prepared to rain death in the form of an avalanche, the original Brain Wave reached out from Limbo and pulled the two heroes to safety in that gray realm.  When the JSA returned to the Ultra-Humanite's lair, the Infinitors followed and defeating their mentors, were in turn subject to mind blasts by the Ultra-Humanite.  Before the criminal could complete his revenge, the combined powers of the two Kings and the Star-Spangled Kid open a rift into Limbo and pulled all the combatants within.  The enraged Humanite engaged in mental battle with Brain Wave but when the senior villain was distracted by a fear of injury to his son, he was mortally wounded by his adversary.   Before dying, he telepathically transferred much of his mental powers to his son and King Jr, then turned and re-engaged  the Ultra-Humanite.  Recognizing the superior powers of two mutant minds combined, the Humanite fell in terror before being reduced to a vastly unpowered mind trapped in the body of ape.  King Jr. would then left to mourn a father with whom he would never fully reconcile (Infinity Inc #5-10).