Benjamin indeed was to remain with Judah; those being the two tribes left to Solomon’s son; with God’s chosen tribe of Levi being scattered throughout all of the twelve tribes.
Benjamin would be a war making people which would dwell together with Judah.
Historically we find Benjamin a sore trouble to Israel during the Judges period, at one point coming within a shadow of complete eradication in war with Israel. Then when God rent the ten tribes of Israel from Rehoboam, Benjamin was left as part of the Kingdom of Judah to remain bound to Judah to this very day and coming under God’s 40 year blessing period for Judah (Ezekiel 4).
Modern Benjamin is clearly NOT Norway as some have thought
Deuteronomy 33:12 And of Benjamin he said, The beloved of the LORD [Judah] shall dwell in safety by him [Benjamin and Judah will dwell together]; and the Lord shall cover [preserve] him all the day long, and he shall dwell between his [Judah’s shoulders, meaning to remain united with Judah] shoulders.
When the Ten Tribes were separated from Judah, Benjamin remained with Judah (1 Kings 12:21, 1 Chron 11:1 and 2 Chron 34:9).
Genesis 49:27 Benjamin shall ravin as a wolf: in the morning he shall devour the prey, and at night he shall divide the spoil
This does not mean that Norway is not Israel, in fact it opens the way for a better understanding of the prophecy concerning Naphtali inheriting the West and the South.
Deuteronomy 33:23 And of Naphtali he said, O Naphtali, satisfied with favour, and full with the blessing of the Lord: possess thou the west and the south.
Naphtali inheriting both the West and the South allows for Naphtali to be split into two parts or nations.
I have been looking deeper into the matter and it does appear that the British Israel Society is accurate on this point. While I do not agree with everything these folks present on every issue, I find this article on Naphtali to be correct. There were two migrations of the White Huns [Naphtali: Nephthalites] one group settling Norway [the West of Sweden] and the other group settling in Sweden [the South of Norway].
Note that “the west and the south” is also an Hebrew idiom for “on the sea coast” which also fits both Norway and Sweden. Norway and Sweden being Naphtali fulfills both the idiom of the sea coast and the prophecy that one part would be in the west and the other part would be immediately to the south.