When trying to get a Top Secret clearance to become a 31D, would it be a problem if my father is a citizen of Spain?

Short answer: Having an immediate family member who is a citizen of another country is not a defacto disqualifying situation, but it could be based on your relationship with them and how much they "exercise their citizenship of another country".

It all comes down to the relationship you have with your father and how much influence he has over you. If, as I expect, you have a close and continuing relationship, then it then becomes dependant what relationships your father has with Spain, the government/citizens of Spain, why he's a Spanish citizen in this country, etc.

The sole purpose of a security clearance determination is to decide if it is clearly consistent with the national interest to grant or continue a security clearance for an applicant. The government's concern is summed up in the guidelines around access to classified information (DoDD 5220.6). Specifically Guideline B about Foreign Influence:

"The Concern: A security risk may exist when an individual's immediate family, including cohabitants, and other persons to whom he or she may be bound by affection, influence, or obligation are not citizens of the United States or may be subject to duress. These situations could create the potential for foreign influence that could result in the compromise of classified information. Contacts with citizens of other countries or financial interests in other countries are also relevant to security determinations if they make an individual potentially vulnerable to coercion, exploitation, or pressure."

So, can it affect your ability to get a clearance? Yes. Will it? That is a very subjective question and every situation is unique. If it's a case where "He's a dual-citizen of Spain but hasn't been back to the country in over 15 years and doesn't have any contact with other Spanish nationals" it likely would be minimal. However, if it's one where he's a citizen of Spain, does work for the government of Spain, and has a close relationship with a government official - that's an almost guaranteed denial.

Everything else is probably going to fall in-between and it's going to be up to the adjudicators to determine how much of risk he has of putting the interests of Spain ahead of the United States, and if that makes you potentially vulnerable to coercion, exploitation, or pressure based on your relationship.
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* DoDD 5220.6 - https://www.esd.whs.mil/Portals/54/Documents/DD/issuances/dodd/522006p.pdf

I would say no problem. My Honduran Cousin was the deputy ambassador or deputy chief of mission of the Honduran embassy in Washington DC and later Ottawa, Canada. I was applying for a top-secret clearance because that is required to be a Civil Affairs Officer. Spain is not a hostile country and it is part of NATO and the European Union.
Others here can give you more factual information. I don't see it as a problem as long as you put it down. If he was part of the ETA ( A Basque separatist terrorist organization) Then this could be a problem.

If you go in as military police like I did originally, You will get a Secret Clearance and that's easy! I was a 31 Bravo and later a 31 Alpha. I just retired from the Army Reserve two years ago.
Let us see what others think.
MSG Joseph Cristofaro COL Randall C.


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Without knowing anything about your father I'd say it might delay the process a bit but shouldn't keep you from getting one.