Board Thread:Skyrim/@comment-109.221.212.147-20160403101052/@comment-1746153-20160406151313

^ It is random, it picks NPCs with a high disposition towards you (since small things can raise disposition, it can cause odd people to turn up, like some Jarls, even if you've never met them but did some quests in their hold), that are in the potential wedding guests faction. In the unpatched version of Skyrim, it sometimes caused corpses to appear at weddings (like if your housecarl died). That said, my wedding guests are usually my kids and housecarls (they take priority maybe?).