WARNING: The following contains spoilers for Aquaman/Green Arrow: Deep Target #6 now on sale from DC Comics.
One of the most shocking aspects of Aquaman/Green Arrow - Deep Target is how messy the timestream has become, resulting in both Justice League members swapping powers and histories. It was all thanks to the sinister General Anderton and his organization, Scorpio, tampering with the past. The goal was to shape a reality until it became their version of a true paradise.
When it was nearly too late, the lizard-like Anderton realized he had made a mistake. To fix things before they went any farther, he teamed with the heroes to disrupt the timeline he created. However, while they seemed to have reset the Earth chronologically, one hero got his own version of Flashpoint, complete with a mini civil war.
When Arthur and Ollie barrelled through time in Issue #6 (by Brandon Thomas, Ronan Cliquet, Ulises Arreola, and Josh Reed), they found a world filled with human-monster hybrids, which is inspired Anderton to redeem himself. However, when everyone's memories reconciled, something was off with Aquaman. Ollie didn't take it on too much because he had bigger fish to fry.
He used Martian Manhunter to secretly mind-probe both versions of Anderton, and their lackeys, suspecting something was still off given the lizard-like general continued to exist. But when he tried to reach Aquaman, he could not raise his teammate. Concerned, Queen travels to the Justice Leaguer's kingdom. Upon arriving, GA is shocked to find Aquaman unhappy to see him. So unhappy, in fact, that Arther unleashes the guards upon Ollie with instruction to end the archer's life.
It seems the "fixing" of the timeline instead deposited the heroes in a Flashpoint-style situation. In Arthur's case, slight tweaks to his past accumulated into significant changes in the present. In this new reality, his mother, Atlanna, got him back from his surface-dwelling dad, Tom Curry. She then, apparently, groomed him and her other son, Orm, to be co-kings. It's why Arthur's sharing the throne, suggesting Orm never became Ocean Master. This gave Arthur the royal family he wished he had. However, as Ollie senses, it is unlikely that the changes are localized only in Arthur's life. If Aquaman doesn't work to reset things, there's no telling what else will be wrong with the world.
With Green Arrow outnumbered at the moment and one issue to go, he might not be able to rely on the other Leaguers, though, because they could be compromised too. This does create the possibility he'll leverage Mera and other loved ones wiped from Aquaman's mind to get the king to do the right thing. But, ultimately, it'll still be a tragic decision that'll rob Arthur of the dream childhood and brotherly love he always wished he had.