Arthur Joseph Curry (aka A.J.) is the son of Mera and likely Aquaman. Shortly after Arthur Jr died Mera was taken by Thanatos (who she thought to be the real Aquaman) to his home in an evil purgatory water-world realm known as Netherspace. Approximately nine months after she was taken Mera gave birth to A.J. while his true father could easily be either man it is assumed to be the real Aquaman. Raised by Thanatos in Netherspace his body is not accustomed to the passage of time in the New Earth universe.
In search of Mera, Aquaman comes to the realm and finds her with Thanatos and A.J. but feels nothing for the boy who could be his son. He does battle with Thanatos before a judgement tribunal, but when he refuses to kill Thanatos the evil judges decide to condemn Aquaman to remain in the realm while Thanatos is free to be Aquaman in the New Earth universe. Aquaman prays to his father, Atlan, who hears his call and opens a portal through which the family can escape. Upon escaping A.J.s body begins to rapidly age. Knowing A.J. cannot live outside of the realm he was born in Mera grabs her son and leaps back through the closing portal, abandoning her recently reunited husband, to be with her son.
Mera became the queen of Netherspace and A.J. grew up to be hero and defender of the realms under the name Aquaman. When aliens come to steal the water from their world A.J. seeks out his father for help. Under magic protection from rapidly ageing, it was difficult to keep his mind clear and while concentrating on remembering "Aquaman" his mind clouded up to the point where he believed himself to actually be Aquaman. When he got to Poseidonis he found the real Aquaman and challenged the "pretender". When Aquaman inevitably defeated him the magic protection wore off and he began to rapidly age again. The truth behind who he was and why he was there came out and they returned to Netherspace too defeat the invading aliens.
With victory in hand Aquaman was once again reunited with his estranged wife and he begged her to return home with him but being queen of this realm and having a son unable to leave she insisted on staying. A.J. wanted to see his parents happily together again and pushed her through the closing portal giving his mother with no choice but to leave him and return to Atlantis.
Having voluntarily been left alone, A.J. remained in the Netherspace as King and hero Aquaman, he was never been seen again.