Most of us gentiles who are not noahides don't believe in the rabbinical doctrine of how Jewishness is transmitted (only from Jewish mother or from orthodox conversion). Some of us get from the Bible that it is paternal descent, not maternal descent. Others think of Jewishness like Italianness or any other nationality. What makes someone Italian is not completely clear. Most would agree that someone with only one Italian parent is Italian and that someone with only one Italian great grandparent is not Italian. But where you would draw the line between Italian and not Italian is not clear. Having a sense of Italian identity probably counts for something too. If someone has a sense of Italian identity because of their only Italian great grandparent, then perhaps they are still Italian. But someone with no Italian ancestry who was born in Africa or China and has never met anyone of Italian descent but had a sense of Italian identity we would call delusional.