Funnily enough, there are probably places where no one would bat an eye about your being both men but where you'd run into an incest law. I think most locales will tolerate a half-first-cousin though.
And I am sure that on some planets you could make that argument and have it go through, and meanwhile somebody somewhere is hysterical that a pair of fourth cousins twice removed are considering holding hands. Big galaxy.
No, it'd probably just come up on some sort of paperwork and you'd have to lie. Marriages in societies without soul grafts involve paperwork.
Before or after the party and definitely not simultaneous with the consummation.
This'll vary by locality but paperwork indicates legal marriage, party indicates social marriage, and you try to have them around the same time.
So a very small party. Sigyn might want to come if you'd have him, after I've told him this whole stupidly long story.
You'd like him. He's very weird, but you can find reasons to hypothetically like almost anybody so I think you'd be able to actually like him.
Well, if they come around later you can have a five hundredth anniversary vow renewal or something like that.
I'm not going to argue with you on the appeal but unless Quendi biology spits in the face of science it's not impossible, and that's if you don't want to adopt.