I'm being more than a little fuzzy-headed this evening (allergies, meds, blah), but am I really being paged into this thread to discuss how to ripen bananas? I mean it's not that difficult, all you need is a brown paper bag and...oh wait, let me read over the last few posts a bit more slowly. :)
It's usually fine to get foreign sims to join your household while in their world and bring them home with your traveling party, but I wouldn't marry them while they are still not part of what the game is considering the active homeworld. It's much safer to do the wedding in a homeworld of which both sims are full residents. And I would strongly suggest having NRaas mods in play that help bypass and get through game breaking errors and sim corruption that can happen in many of the ways these things can be done -- those would be ErrorTrap, Overwatch, Traveler, and RelationshipPanel. Especially Traveler though on the ensuing travel transitions.
MasterController can also be used to yank not actively being played sims out of one world and into another as full-fledged residents, but the other sim has to not have a presence in the current homeworld yet, not even as a visitor/tourist, and that's more of a brute force approach. I still use it at times especially when large numbers of sims are involved in the desired world transfers.
A sim who is visiting a homeworld as a guest/tourist should never be asked or forced to move in while in the visiting state, they are in that case a scaled down mini-sim representation of themselves and not the full version, unless again mods are present to protect that sim from data corruption.