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Spain — Marriage
Possible
Everything here turns on one fact, and it is usually settled by looking at a single document.
The one-year route requires a spouse who is a Spanish citizen. Being from Spain, having been born in Spain, or holding a Spanish residence card are all different things, and only citizenship counts. Someone can have lived in Spain their whole life and hold another nationality; someone can have left decades ago and still be Spanish.
What settles it: a Spanish passport, a DNI, or an entry in the Spanish Civil Registry. A NIE is not proof of anything — it is a tax and identification number issued to foreigners, and people frequently mistake it for evidence of nationality. If your spouse has a Spanish passport or DNI, they are Spanish.
If it turns out they are Spanish, the route is one year of marriage plus one year of legal residence in Spain, which is the shortest path Spanish law offers. If they are not, you are on the ordinary clock — ten years for most nationalities, two if you are a national of a Latin American country, Andorra, Portugal, the Philippines or Equatorial Guinea, or if you have Sephardic ancestry.
There is also a possibility worth raising: if your spouse has Spanish ancestry but has never claimed it, they may be able to. That would change your position as well as theirs.