You can't always go by surnames. My surname is French, my dad's mom's is Norman Highland Scottish, my mom's dad's is English or Lowland Scottish, and...
People on here are too focused on genetic calculators that don't actually tell you that much. I can tell what race someone is or if they're a mongrel...
The best way is to look at transits, which slightly dim the starlight output recorded over time when an exoplanet get in front of it. It can be rare...