It happened long ago, on a place called Earth-2, where the original Batman (who was a member of Justice Society of America) and the Golden Age Catwoman lived....
The Autobiography Of Bruce Wayne
Batman worries about being alone as one of Bruce Wayne's former girlfriends gets marries, and, thanks to a recently paroled Scarecrow, that fear manifests, as Robin, Batwoman, then Alfred, Gordon, even Lois Lane and Superman disappear. Batman goes for help from an old enemy, Catwoman, serving time as Selina Kyle after turning herself in (and claiming amnesia for most of her time as Catwoman). During their search for Scarecrow, the two open up to each other about how much life had hurt them, and that they had both needed someone...so that they both conquered their fear of being alone by trusting each other. The story ends with a quick summary of their wedding, as well as the events which happened in the decades following.
The Kill Kent Contract
This tale starts with Clark and Lois getting an invitation of Bruce and Selina's wedding (via Batplane, no less), and the pair heading to Gotham City to attend (revealing Lois knows both parties secret identities as well as how Selina gave up, about her brother Kyle, the King of Cats). A phone mix up allows Lois to hear that a plot to kill Kent is afoot at the wedding. The ceremony shows Dick Grayson as Bruce's best man, Karl Kyle giving Selina away, and Bruce's butler, Alfred Beagle (the Golden Age version of Alfred Pennyworth), Com. James Gordon (with wife Barbara and son Tony). Afterward, at the reception, Clark and Lois meet Harvey Kent, former Gotham District Attorney (and Two-Face, before cured with plastic surgery), who as the Kent who was the target.
Sadly, this tale, like most of the Mr. and Mrs. Superman tales other than Lois and Clark's wedding from Action Comics #484, has not been reprinted, but this whole run from Superman and Superman Family, along with the Action Comics issue cries out to be collected, as writer E. Nelson Bridwell really fleshed out the differences between the Earth-1 and Earth-2 versions of Superman (and Batman) with entertaining tales of a married Clark and Lois set in the 1950s.
From Each Ending....A Beginning
The majority of this issue is about Helena, and Bruce and Selina's life at that time, but this does have that first flashback to her birth in 1957, as well as a little time of her growing up, as well as establishing many of the guests at Bruce and Selina's wedding, setting up for the later tales which help fill in the holes of the details. The issue also introduces Silky Cernak, and the catastrophe he will introduce into the lives of Bruce, Selina and Helena Wayne in 1976, which the title of the tale suggests, leading to the introduction of the Huntress and her costume which looks like a hybrid of Batman and Catwoman's (though Huntress appeared only days earlier in All-Star Comics #69, technically her first appearance in a cameo in the JSA tale, though this story happened first).
the Huntress reprints from the 1970s/1980s from the back of Wonder Woman as her history shows, almost all her other tales have been reprinted), and in Catwoman: A Celebration of 75 Years from 2015), completing our look back at the first time Batman and Catwoman got married.