Bless these bones

AU divergence from the original story starts really early, during those few first few fights between Sun and Moon, down in that little bunker while hiding from the government. When Moon hits Sun, he accidentally swings a little too hard and shatters part of Sun's faceplate. Moon immediately feels horrible guilt and lets Sun leave without much fuss, wanting to give him space. He doesn't know that'd be the last he'd ever see of his brother.

Sun, instead of going to Golden Freddy, heads back to the daycare to steal Moon's dimensional gun (assume he has one at this point) and uses it to intentionally get himself lost within dimensions, both to screw over Eclipse and not have to ever see his brother again. But, once the anger dies down and it fully settles in what he'd just done... Sun gives up. He gives Eclipse full reigns of his body. He'd just permanently rid himself of his brother and his daycare job that he adored so much, and he no longer saw a point in fighting it anymore.

Eclipse, although initially furious, quickly discovers that Sun just gave him the opportunity to be an interdimensional criminal with basically 0 consequences. He can commit armed robbery at a bank and steal weaponry from the government, and what are they gonna do about it? Arrest him when he's already 15 dimensions away?

It doesn't take long for the emptiness and deep loneliness to settle in. Seeing as he never made Lunar, he instead turns to Sun, goading him into joining. It takes a while, but Sun-- lonely, miserable, vulnerable, and deeply missing his brother that he loves hates-- gives in... And so begins his complete dissociation from who he used to be. He's not Sun anymore, he's not the happy-go-lucky daycare attendant anymore, he's Aphelion the heartless criminal! Stop- stop acknowledging that he still goes out of his way to avoid harming kids at all costs. He's a heartless criminal! (Eclipse renames himself to Zenith to match with Aphelion renaming himself)

Things change with time. 1.5 years in has Zenith and Aphelion sharing a rocky, unsteady truce. It's not like they have anyone else who's remotely on their side. They're running across dimensions, stealing what they need and making enemies all over. But who cares? Neither of them can trust or rely on anyone; not even each other, outside of their truce. 4 years in and they've adopted each other as twins, having (mostly) let go of their past grievances altogether. It's not like they have anyone else. They've started to gain a reputation among fellow interdimensional travelers as a dangerous person(s) to avoid. 8 years in and they're being chased down by the people they've crossed in other dimensions. A version of Monty grabs Aphelion by the leg and snaps off the lower half of it. It's the first time Aphelion didn't feel very bad when Zenith kills someone. They get a peg leg instead of a full replacement, because they're paranoid of being hunted down and are working with what they have. 11 years in and Zenith discovers how to travel the fabric of reality in between dimensions, they just need to stay in the tiny boat he designed for it. That makes it very, very hard for anyone to track them down.

22 years in and they now have a full fledged pirate ship. Aphelion insists they start dressing and talking like pirates, because if they have the ship then they've gotta play the part! Zenith thinks it's lame until he helps style an outfit he thinks actually looks really cool... He doesn't bother with the accent though.

25 years in and they steal Moon's daycare security AI. Well, no, Zenith steals it (Aphelion felt anxious even being moderately adjacent to any version of the daycare again). Zenith straight up opens a portal behind the arcade machine and steals it, then reprograms it to be loyal to them. The AI earns the new name and title of First Mate when it evaporates someone and saves their lives a few months after being sto- ahem, "recruited." First Mate is immediately integrated very closely into the ship's security systems, and Sun practices magic to put protective barriers around it in addition to all the firewalls Eclipse programmed in.

26 years in and they have a version of Lunar follow them onto their ship, demanding they return whatever it was they stole. Zenith ties Lunar up and threatens their family to pay ransom, unless they want Lunar to walk the plank (who knows what'll happen if you fall in the space between dimensions?). Aphelion ignores the guilt of playing along, and Zenith tries to shake off the feeling that he hurt someone who should've been important to him. Oh well.

30 years in and kidnapping people from random dimensions and threatening their family to pay ransom has become quite normal for them both. Aphelion has grown highly proficient with his sword, and Zenith loves the power trip of pointing his gun in people's faces when they start mouthing off (that's no normal flintlock pistol-- it's custom made by him and it can blow a hole straight through titanium). They've used the money to upgrade their ship and equipment significantly. Aphelion's an even worse alcoholic than Zenith is, and they sing sea shanties together when they're not busy kidnapping people (First Mate disables the wheel controls whenever they start drinking so that they don't go drunk driving their ship). They're both so, so deeply lonely despite how co-dependent they are at this point. They'd rather drink and steal more things than look directly at the festering feelings in their head.

31 years in and it's their first time kidnapping that weird "Tara" (or sometimes "Earth") girl they've had pay up ransom a handful of times. She's so... So nice to them. It shakes something in Aphelion that he thought he'd already drowned out completely, and Zenith doesn't know how to handle it. They decide to put her back in her dimension before her family has a chance to pay up the ransom. They never kidnap another version of her again, and they might be a little more willing to forgive a payment that falls a little short of what they demanded if it's a version of Tara talking to them. (She also tried to give them therapy and they're scared of therapy)

... Which brings us to now. It's been 32 years since Aphelion first left his own dimension and they're better than ever! Just ignore the raging alcoholism... And Zenith getting their insides coated in ash from smoking all the time... And them temporarily kidnapping people on a whim, without demanding ransom, just because of how desperate they are for any kind of company outside themselves (First Mate isn't very sociable, unfortunately)... And them freezing up at the slightest hint of physical contact, because it's been literal decades since they've gotten so much as hand holding... And the extreme paranoia... And the trust issues... And the co-dependence... Ahem. Anyways.