"what is the nationality of my father and forefathers according to the true law of God & the Bible?" Someone asked me and I don't know the answer
Do you mean the forefathers of your flesh (bloodline from Adam)?
It's difficult to know the nationality of your forefathers from Adam without knowing their ethnicity, whether they intermarried, whether they ever traveled to a new nation to settle down, etc. But
Genesis Chapter 10 gives the table of nations from Noah's sons: Shem, Ham and Japheth.
Because there has been so much intermarriage (and conquering) between the offspring of these three brothers one can't really rely too much on one's external characteristics to determine from which brother one comes...and at this point (in Christ) it's really irrelevant. But the following is still true about Noah's sons:
Shem
Shem means "name", so those from Shem are called Semites or "people of the name". Anyone from Abraham's fleshy bloodline - Ishmael, Medan, Midian, Isaac - is a Semite (or Semitic), not just the descendants of Israel (the Jews). Even cousins like the Assyrians were Semitic. Assyrian Empire & Kingdom of Israel.
Ham
Ham means "sun-kissed" (or in its most basic meaning, "burnt"), so Ham was the progenitor of those of darker-skinned characteristic. These are the African nations like the kingdoms of Egypt (originally called Mizraim until Alexander renamed it), Ethiopia, Kush, Canaan. The evil king Nimrod (who led the world to build the tower of babel) was also a descendant of Ham.
Japheth ('Yah-pet')
Japheth means "Yah entices/attracts"; these were the fairer-skinned cousins of the world's family. These are your original European people: Ashkenaz (Germans & Russians), Magog (Scythians [Ireland?]), Tubal (lberians [Italians, Spanish]), Javan (Ionians/Greeks). Alexander the Great. The Greco-Roman Empire.
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Again, in Christ this is all pretty moot because anyone who has faith is a seed of Abraham. But then again...anyone *not* in Christ (which is much of the world) is still a descendant from their perspective forefather.