* Last names can be common across multiple cultures and countries. "Lueras" might be found in Spain, Portugal, or even parts of Latin America due to historical and linguistic influences.
* People can have multiple nationalities. Someone with the last name "Lueras" could be Spanish, Portuguese, or have a different nationality entirely.
* Last names can change over time. A family with the last name "Lueras" may have originated in one country and migrated to another, adopting a different nationality over generations.
To understand someone's nationality, you need more information than just their last name.