I am from Japan and currently staying in the USA. I am going back to Japan in June and plan to come back in August. My fiancé(American citizen) and I are planning to get married in September after I come back. I have a daughter who is 17 and she is going to be 18 in September.
Yes, if you get married before your daughter turns 18, her citizen step-father can sponsor her for a green card. Please see http://www.avvo.com/legal-guides/ugc/green-cards-for-family-members
Mr. Shusterman's (former INS Trial Attorney, 1976-82) response to your question is general in nature, as not all the facts are known to him. You should retain an attorney experienced in immigration law to review all the facts in your case in order to receive advice specific to your case. Mr. Shusterman's statement above does not create an attorney/client relationship.
If your intent is to marry a U.S. citizen in September in the U.S. then you must enter on a K-1 visa. If you enter on a visitor visa, get married, and then attempt to adjust status, it may appear that you committed visa fraud by entering the U.S. with different intent than the visitor visa. It is not likely that you could obtain a K-1 visa before August due to processing times. If you wish to get married in September, it may be safer to do so outside the U.S. and then apply for a green card for you and your daughter through consular processing. Or else postpone your wedding until you obtain the K-1 visa.
You cannot come into the US on a temporary visa or VWP with the intent to marry a US citizen and staying in the US. The US government would be alleging that you commit immigration fraud.
You cannot get a K-1 visa by August. The process takes much longer than 4 months.
On another hand, getting married in WA is relatively simple and quick. You two can be legally married to each other by next week's Tuesday if you are willing to have a simple wedding ceremony.
Furthermore, things often happen unexpectedly. That September wedding may become delayed for many reasons.
Getting married now would ensure that your daughter can immigrate through the husband.
You and the future husband should review the specific facts with attorneys.
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