Board Thread:General Discussion/@comment-66.249.88.162-20150806044958/@comment-6881629-20150807085957

If a npc that can't usually be married shares their voice with one that can usually they can be made marriageable with the console and the marriage dialog from the voice actor will be used, for a unique voice like Serana even if you could use the console to add them as a marriage option they don't have any voice clips for marriage dialog (with Serana being so popular though there is a mod that mixes up her existing dialog to actually make some).