You must be married before you file I-918 to include spouse in U visa petition. Of course, you can wait 3 years to get greencard (with U visa backlog probably in total 5 years), but if the spouse is without status in US, why risk her deportation? Since you can't add a spouse to petition if you married after filing I-918, can you cancel it and file the same petition again with spouse now included to solve the issue? If not, what law would prevent this? Are you prohibited from submitting another U visa on the same grounds with corrected I-918, if YOU cancel old petition before it is approved? A withdrawn petition can not be denied so you should be able to submit, right? Any thoughts?
I highly recommend you consult with an immigration attorney directly before you do anything
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