(Okay so I don't know where this is from but I know the actor and I know he has a reputation for looking way younger than his actual age so I'm guessing since he looks about y.o. here...he's probably IRL....late teens? :P )
As Mark stood there in the sun, he seemed to glow to Sebastian. In that moment, Seb realized he had found the one person he could find peace in, not get tired of, spend the rest of his life with. And he was completely fine with that.
Groom attire: Dress as a royalty, perhaps as High King Peter or Prince Caspian in the movies. Knee high boots, a velvet tunic with mandarin collar, hose or slightly tight pants and a cape. This totally goes with your theme, right? Kidding!!