P. Matot: Umikneh Rav liv'nai R'uvein, Gad - So How did M'nasheh get Included?

R'uvein and Gad approached Moshe Rabbeinu requesting TransJordan. When Moshe acquiesced, he added Hatzi Shevet M'nasheh. Why?

Below is a an answer based upon the structure of the Tribes throughout Sefer Bamidbar - here is that dynamic at work

When Levi drops out of the "tribes" a shuffle occurs in Parshas Bamidbar, Nasso, B'haalot'cha. *

1. Gad is promoted to Honorary Ben Leah, camping with R'uvein and Shim'on

2. Yosef is divided into Two, Ephraim and M'nasheh to restore the number to 12

The 4 camps now are structured as follows

East - 3 from Leah
South - 2 from Leah plus Gad
West - 3 from Rachel
North - 3 from the "sh'fachot" - 1 from Zilpah, 2 from Bilhah

Levi was now in a circle inside
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When R'uvein and Gad chose TransJordan, then we have

20% of Leah
25% of the Sh'fachot
0% of Rachel

To Remedy this Moshe takes 1/2 of M'nasheh which comprises about 25% of Rachel - thereby restoring a balance of Imahot. [Counting Bilhah/Zilpah as a unit]

Why M'nasheh and not Ephraim? I'm not sure - but perhaps it is since he is the b'chor and so are R'uvein and Gad.

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* Note whenever Levi IS counted in the 12, Joseph is reunited.

Shalom,
RRW