Pym is the son of Hank Pym & the Wasp. He was raised by Iron Man alongside his friends Azari, James Rogers , and Torunn. Together they formed the Kid Avengers and later added Hawkeye to their team. The Kid Avengers brought an end to Ultron's tyranny together with the help of Iron Man, Vision, and the Hulk.
Henry Pym Jr (Big Man) was created by Tom DeFalco and Ron Frenz and first appeared in A-Next issue 12 (1999). Another version of Henry Pym Jr first appeared in the pages of Avengers Vol.4 issue 1 (2010) as part of a band of kid Avengers.
Major Story Arcs
Henry Pym Jr is extremely adept with technology and can grow like his father, and can shrink and fly like his mother as well as shoot power blasts. He is very young and innocent, but a strong fighter nonetheless. He is good friends with Azari, who tends to put up with his naivety better than the rest.
In the alternate future of the MC2 Universe, Henry Pym jr was known as the superpowered Big Man. He and his sister Hope Pym joined a team of villains and started calling themselves the Revengers. As a part of this tean, Big Man and his teammates fought the Avengers. Eventaully Big Man redeemded himself and became a hero. He even joined a government sponsored superhero team.