Wedding Day by Riothouse http://www.fried-potatoes.com/fanfiction/viewstory.php?sid=233
We’re watching a wedding take place, through the eyes of one of the guests – who seems sad and angry that the wedding is taking place. Who is this guest, whose thoughts we share? Who is getting married?
Hold by Sleeps With Coyotes
On the day marriage equality is allowed in Germany, Klaus goes to England and asks Dorian to marry him and move to Germany. Sadly, this story is not available online at present. Sleeps With Coyotes is a fabulous writer, and this story is full of great insight into what motivates both Klaus and Dorian.
Cakes and Ale by Torch (aka Flambeau) https://archiveofourown.org/works/190516
Klaus and Dorian wake up the morning after celebrating at Z’s wedding, hung-over and dishevelled, not sure just what they did the night before. In spite of their hangovers, they work out what happened … and come to an agreement.
Stiff Upper Lip by Yoiko https://archiveofourown.org/works/1520591
Klaus is getting married – and it’s not to Dorian. A sad-sweet story about letting go.
... And here are two other recs I’d like to sneak in, which are about engagements rather than weddings:
Engagement by Mersault … which doesn’t seem to be available online just now.
“Marriage was really only an extension of his family duties. He supposed he was fortunate - Anna was young, pretty, pleasant.” Does anyone know of an online source? (It's so sad when archives disappear off the web.)
The Cuckoo's Nest by CassieIngaben https://archiveofourown.org/works/43428
Klaus’s fiancée has news. It doesn’t have the effect she’s expecting.
Unholy Matrimony by Tzigane and Yoiko
A lighter story from the Caffiends crew, in which Klaus and Dorian have to enact a Vegas wedding as to not blow cover. It doesn’t end well for Klaus. Mischa and his KGB cronies, meanwhile, attempt to spy on the newlyweds and leave them gifts. Klaus can’t catch a break, but Dorian does. Crack-fic. Warnings for terrible decor, edible clothing, champagne shenanigans, and Klausian death-threats.
Getting Married Is A Hell In The Making by Chemcat
Klaus finally decides to get married, and Dorian is invited. Another crack-fic. Three parts! It should totally be canon...
The Happiest Day Of Somebody’s Life by Telwoman
Klaus’ father falls in love again, and Klaus has a wedding to attend. Poor Dorian has to hear rumors about a wedding at Schloss Eberbach, so he goes to cause trouble.
Klaus getting married is mentioned, as is his wife... and Dorian.
Smoke by Filigree
Klaus contemplates his loves, his heath, himself, and his choices as he lays badly wounded. Very ambiguous. I can’t stop thinking about what happens next!
n A Good Wife by Amity33, Klaus drafts Dorian to play the role of Klaus's wife, if that counts. :)
My favorite wedding story (well, almost, at least), would be Kadoriennes Decent Proposal.
Klaus and Dorian undercover as a married couple in cranialaccessorys Hesitation Waltz
Oh, and Dorian is married (to a woman!!!) in the tantalizing preview The Man In the High Schloss by Cassie Ingaben.