How to determine if an NPC is available for marriage

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In the vein of Are inter-racial marriages frowned upon? – Pete Hines, Bethesda's VP of PR and Marketing, when asked if Skyrim would support gay marriage said the following:

You can marry anyone…Not any NPC, just mean any male or female.

So obviously some NPCs are off the list. I assume I can't marry Jarl Balgruuf, but what about Irileth? What about the Graybeards? What about already-married NPCs? Is it any "important" NPC, or is it more or less than that?

Has the Skyrim Creation Kit shed any light on how to determine this?

Best Answer

NPCs who can be married will be part of a faction, marriage-faction.

The console command addfac 19809 1 while having an NPC selected will make them eligible for marriage.

For scanning through info in the Construction Kit, look out for

marriage-faction

and the faction ID

19809