Samaritans weren’t Israelites to the Jews, because they had lost their lineage and intermarried with the surrounding peoples. Just look at Jesus’ interaction with the Samaritan woman at the well.

And then look at how Jesus’ disciples interpreted the command in relation to Greeks, Ethiopians, and… even slaves (the entire letter to Philemon deals with exactly this point, instructing the non-Jewish Philemon to treat his escaped slave Onesimus as a brother/kin, not as Romans treated their slaves).