The following contains major spoilers for Batman: Beyond the White Knight #2, on sale now from DC Comics.
In the Batman: White Knight universe, Bruce Wayne and Harley Quinn have had a unique yet embracing relationship. They've grown to care for each other, stemming from Harley helping Bruce and his clan stop Joker. It was tragic though, because no matter what she loved the Jack Napier side of the clown, and ironically had to kill both personas to save the Bat.
Nonetheless, Harley was at peace because it meant she could have Joker's twins in peace and live a life without chaos. Most of all, she kept visiting Bruce after the Dark Knight turned himself in during Curse of the White Knight (by Sean Murphy, Matt Hollingworth, and AndWorld Design), letting him know he wasn't alone despite being behind bars at Stonegate. Batman: Beyond the White Knight #2 (by Sean Murphy, Dave Stewart, and AndWorld Design) revealed their bond took an even more shocking turn, with Harley spilling the beans she's actually Bruce's wife.
The bombshell came after Jason Todd helped Bruce escape jail to go stop the tech-Batman roving around Gotham with no control over the new suit. However, the ex-vigilante ended up at a safe house with a hologram of Jack around only he could see. Jack made it clear this A.I. version of himself wanted to help Bruce, so he could become whole again and be there for Harley.
Interestingly, this new Bat-cave with tech and equipment was in the home Bruce left for Harley. As a result, when she showed up at the haven, she flipped out on the Bat. She hated how Bruce fled because she didn't want him becoming an enemy of the state, especially with Powers warping Dick Grayson's GTO police force into a group of brutal tyrants. Shockingly, she confirmed Bruce stopped visitations for years after Jack's death and also after they took Azrael down.
It's then and there she confessed Bruce shouldn't have been sneaking around because they weren't just best friends, they were married! The revelation left the invisible A.I. stunned and fans trying to piece together when this could have happened. And more so, why. It could be for financial reasons, allowing Bruce to keep personal expenses after he gave his inheritance back to Gotham to rebuild the city.
Then again, romantics are positing maybe they did get hitched, hoping a romance wouldn't be doomed. If that's the case, then the next issue has a lot of explaining to do to fill in the time gap. Admittedly, a union's an interesting notion and one that would be nice to explore had Jack not been in the picture. After all, Harley helped heal Bruce and remind him his Caped Crusader wasn't a failure; while Bruce showed Harley she could be a hero. Ultimately, only time will tell what sparked this major change in their dynamic and the consequences to follow.