the Jews of the first century didn't seem to include them.
That was the point, dear BC: THEY didn't... but Christ did. (Again, peace to you... if something doesn't make sense because a word missing, misspelled, etc., please overlook and/or ask me and I will clarify!).
The Jews all but dismissed the other 10 tribes, the Samaritans. And they still do, down to this very day. Who, though, are the "Jews"? The "Jews"... or "Yehudi"... or those who descended from/joined themselves to... is "Judah". "Judah" is those who belong to/descended from the tribe of Judah... and the tribe of Benjamin. Benjamin joined up with Judah for the purpose of preservation, after they were almost completely wiped out by the other tribes when they heinously gang raped a concubine... who died as a result (wait for the opposers who will blame this act on JAH... while completely overlooking the culpability of the men that did it. I digress.).
Some (including the early Jews) like to say that the Jews are "all of Israel" and/or the other ten tribes were "lost." But that's not entirely true. Because salvation comes THROUGH the Jews... and because the temple was in their capital city (Jerusalem, the capital of the land of the Jews, Judea)... the Jews represent the entire nation [of Israel]... FIRST. But they do not represent ALL of Israel, as they claim.
How does do 10 whole tribes of people go missing? When they are exiled by and to an enemy (here, Assyria)... and then take up existence in a land/area other than Judea (here, Samaria, where they returned once their exile and capitivity ended)... AND, most importantly... don't worship at the temple built and via the system established... by their mutual forefather of ALL of the tribes, BOTH Israel AND Judah... Solomon, the son of their greatest king... David. Hence, then the 10-tribe kingdom of Israel was captured by Assyria... and subsequently exiled... the tribe of JUDAH was pretty glad about that! Why? Because they considered their own brothers, the tribe of Israel... their enemies!
Why were these two enemies? It goes back to the split under Rehoboam, Solomon's son. Under Rehoboam, Israel was greatly oppressed. Rehoboam was advised to lighten up. Instead, he took offense (he was Solomon's son after and who were these upstarts to tell HIM, the KING of Israel, what to do?!)... and became even harsher. And so the kingdom divided. Under the leadership of Jeroboam, 10 tribes ("Israel") seceded from the kingship of "David." Out of loyalty to David, though, two tribes ("Judah") stayed with Rehoboam.
Judah... continued worship at the temple in Jerusalem, the capital of Judea... by mean of the sanctioned priesthood (rendered by the few priests from the tribe of Levi who stayed with Judah). Israel, however, took another course: rather than travel to Jerusalem as their forefathers had, they now considered Judah... and anything in relation thereto... as enemies. So, Jeroboam set up worship for THEM at Bethel... the capital of Samaria. But, in violation of the Law... he chose priests from among any of the 10 tribes and not just Levi. The result of this was that, after awhile, false worship became rampant in Bethel. Rather than worship as established under Aaron, they began to worship according to the nations. So they built "high places"... which does not refer to the altitude of the mountainous region in which they worshipped... but the ALTARS (the higher the better, folks thought!) upon which they conducted their worship and sacrifices.
These high places/altars, however, were often built for and used to worship OTHER gods... while also being used as a pretense to worship JAH. And in this way, their worship constituted "spiritual adultery." This "adultery" was the impetus for their capture by the Assyrians and exist into Assyria. In the sight of JAH, they were fornicators and adulterers. He referred to them as "Oholah."
Rather than come to their aid, however... out of brother LOYALTY, if nothing else... the 2-tribe kingdom was quite glad to see their "enemy"... even though such were also their brothers... get their come uppance. And so they stood by and let it happen. They considered what was happening to Israel merely recompense for that nation's false worship. Problem is... Judah turned to doing the exact same thing, even worse. They began taking on the customs and traditions... and then engaging in the worship of the gods... of the nations around them. Eventually, they went ever FURTHER with their fornication/adultery than Samaria ever thought of: they allowed such false worship to take place even in the temple (hence, Ezekiel's visions and proclamations as to what the "shepherds" and priest were doing IN THE TEMPLE. As a result, they (Judah) were constituted as the harlot "Oholibah"... and allowed to be captured and exiled by the Babylonians (Chaldeans).
While Judah (who, Biblically referred to themselves as "Israel" by this time... because they no longer recognized the other 10 tribes) was exiled in Babylon, Assyria released Israel (the 10 tribes) who returned to Samaria. However, Judah (who now called themselves "Israel") never again recognized them as part of the nation. As far as Judah was concerned, THEY were "all Israel," because, their position was that JAH had "dealt" with Israel and pretty much wiped THEM (the 10-tribe kingdom) off the face of the earth. He had not.
So, when Judah (the Jews, who now called themselves "Israel") was released from Babylon... and returned to Judea... their haughtiness would not permit them to recognize or associate with their brothers, Israel... now residing again in Samaria. Because, to add insult to injury, not only were these NOT wiped off the earth... BUT THEY STILL ENGAGED IN WORSHIP AT BETHEL... refusing to worship in Jerusalem. And so the two continued their long-standing rivalry and considered one another as enemies. As it states, "Jews had nothing to do with Samaritans". However, the feeling wasn't entirely mutual... which is why my Lord used a Samaritan in the account of the "Good" Samaritan. There, he gave the lesson of who truly is one's "neighbor" by showing how a Samaritan... a stated enemy of the Jews... gave of himself to help a Jew who had fell among robbers... when the Jews own tribal men (one a Jew, another a Levite priest) WOULDN'T help him.
And this estranged relationship is why the NT often records my Lord involved in matters related to "Jews and Samaritans" and "Judea and Samaria"... versus, say, "Jews and Egypt" or "Judea and Syria", etc.
Now, for Cornelius. Cornelius was the first NON-Jew to receive the promised holy spirit. This is because he was the first of the OTHER 10 tribes, the Samaritans. Because the way opened to the NATION of Israel first... Jews (Judah), then Samaritans (Israel)... and THEN to the non-Israelite nations. Where folks get confused is as to what constitutes "the nations" and/or "Gentiles." Here is how that works:
1. The FULL nation of Israel is made up of 12 tribes
2. JEWS constitute only TWO of those tribes, Judah and Benjamin (although they CLAIM to be the entire nation... from their return from Babylon... and their scribes continued this falsehood when writing the Septuagint)
3. Anyone who is not a JEW (Judah or Benjamin... and a smidgen of Levites who went with them due to service in the temple) is a "Gentile"
4. Thus, along with people who are not Israel by ANY means, people of the 10-tribe kingdom (Israel, which includes the lion's share of Levi) are "Gentiles"
So, then, the "good news"... that was for Jews... AND Gentiles... was to be preached:
1. "In all Judea" (and thus, to the JEWS, Judah/Benjamin);
2. "AND Samaria" (and thus, to the SAMARITANS, Israel); and
3. "To the distant parts of the earth" (the nations who are NOT Jews (Judah) OR Samaritans (Israel)
Those who are Israel... either Jew or Samaritan... who accepted Christ... were the "holy ones" and "brothers" that Paul and others referred to in [the opening of] their letters. The non-Israelites nations are "fellow citizens" of the holy ones.
Now, where is all of this written? Virtually everything I shared here is in the Bible; however, much of it can also be found in secular writings as to Israel's (the WHOLE nation) history and particularly its kingships. This division is what is often confusing for some... for instance, when they read of the kings of Judah... and the kings of Israel (many believe these to be the same - they were NOT).
Rather than give you the verses, I will let you research it yourself first. Start with the division of the kingdom under Rehoboam. Read everything you can about Jeroboam. Look into Samaria... and particularly "Bethel."
Once you've done that, re-read the account of the conversation between my Lord and the Samaritan woman. Think of that fact that Jews "had nothing to do with Samaritans" and then ask yourself, why was this woman at JACOB'S well? A hint: Jacob was the patriarch of the nation of Israel, the nation being named after HIM: Jacob aka Israel, the name he as given after wrestling with an angel. Why would a Samaritan woman be drawing water at JACOB's well? Where WAS Jacob's well... and why was Christ there... and talking to HER? Ask yourself, "Why would he tell HER that SHE could have received "living water" from him... but tell a Phoenician woman that it wasn't for HER... that he had only been sent to "the lost sheep of ISRAEL?"
Then, again, consider Cornelius, an army officer who lived in Ceasarea (look up where Ceasarea is). Then consider the army he served. Many believe and teach that he was a ROMAN army officer - he was NOT. He was an officer "of the Italian band." Italia... was NOT Rome. Rome had its own army (hence, he would been said to have been a Roman army officer. Consider what was Rome back then... and what was Italia... and how the regions were governed. A hint: Rome was a city state, not a city in Italy as it is now. Although Jerusalem was under control of and occupied by Rome, Italia was its own region, not yet under Roman rule (it was coming, though). But look into that, too: Italia, Italian army band, etc.
Start with that and then, if you need, I will share scripture, verses, chapters, etc. But to do so right now... there is WAY too much. Indeed, the entire account of the books of Kings, after Solomon, is about a great deal of this. Unfortunately, most of it is told from the point of view of Judah... because, again, Israel wasn't recognized after their capture and exile.
If you want an EASY way to understand all of this... indeed, even SEE it... then I would exhort you to go to the One who shared it all with me: the HOLY One of Israel and Holy Spirit, JAHESHUA, the Chosen One of JAH (MischaJah). Because all of this had bearing on HIM and HIS arrival. It was critical for folks to KNOW... so that could RECOGNIZE Messiah when he arrived. Fortunately, some did. Unfortunately, many did not.
I hope this helps, dear BC, and, again peace to you!
YOUR servant and a slave of Christ,
SA