Your result
Spain — Citizenship by Descent
Not eligible
There is no Spanish claim by descent here, which takes a moment to establish and is worth establishing quickly.
Spain passes nationality down from a parent, and in one route from a grandparent. It also grants it at birth to someone born in Spain where a parent was born in Spain too. Without one of those, descent is not a route — and neither are the ones people reach for next: a spouse, a sibling, an aunt or an in-law creates no claim in Spanish law, however close the family or however Spanish the surname.
That does not mean Spain is closed to you, and the alternatives are more accessible than most countries offer.
If you hold the nationality of a Latin American country, Andorra, Portugal, the Philippines or Equatorial Guinea, you can naturalise after two years of legal residence in Spain rather than ten — and you will not be asked to give up your existing passport. If you are married to a Spaniard, one year of legal residence in Spain is enough. If you work remotely for employers outside Spain, Spain runs one of Europe's more usable remote-work visas, and time on it counts towards naturalisation. Each of those starts with getting a residence permit, which is the real first step rather than the paperwork people usually begin with.