Britsimon
Super Moderator
@SusieQQQ I guessed that would be the case but thought I'd still ask the question
@Britsimon I've searched these forums the past few days and can only see @cj27 talking about defacto relationships. With the other people you have mentioned do you know if they got married after filling out the DS260 but before the interview? Or did they do it before they even submitted the DS260 form? Thanks.
The defacto relationship is like being unmarried for US immigration purposes. It is no more complicated than an unmarried couple (but with excellent proof that the marriage is not just for the purposes of a easy extra Green Card)
So - simplest option is to get married, then submit the DS260. No need for anything more complicated than that.
It is possible to submit the DS260 as single, get married, then add the DS260 for the new spouse and change the DS260 for the principal. The second option may be faster if you have a low case number.