How would Yosef's additional children have been factored into inheritance?

Question

Bereishis 48:6 refers to what the status of any future children after Ephraim and Menashe that Yosef would have had would be:

וּמוֹלַדְתְּךָ אֲשֶׁר-הוֹלַדְתָּ אַחֲרֵיהֶם, לְךָ יִהְיוּ; עַל שֵׁם אֲחֵיהֶם יִקָּרְאוּ, בְּנַחֲלָתָם

And those born to you after them will be yours. They will be called by the names of their brothers in their inheritance.

Ephraim and Menashe later got separate sections of the land of Israel and inherited as separate tribes. So how practically would the future inheritance of these brothers have worked? Would they have been assigned to be split between either Ephraim or Menashe, or would they somehow have taken from both (Ephraim and Menashe had bordering portions in Israel)? If there would have only been one additional son, seemingly he would have had to divide in somehow.

Answer 1

Rashbam on the Pasuk writes:

ומולדתך - בניך או בני בניך... על שם אחיהם יקראו ולא יהיו שבטים כי אם בתי אבות, כי כל שבעים נפש שהיו בשעת ביאת יעקב בין בנים בין בני בנים היו בתי אבות ולהם נתחלקה הארץ... וכתיב לבסוף: לאלה תחלק הארץ בנחלה וגו' לשמות מטות אבותם ינחלו. וכן בני בניו של יוסף שנולדו אחרי כן יקראו על שם אחיהם בנחלתם והיו בתי אבות, כדכתיב בפרשת פנחס.

And those born to you- your other sons or grandsons... they shall be called in the name of their brothers and shall not be tribes, but 'father's houses' (individual families inside of the tribe), for all of the seventy souls [of Ya'akov's descendants] who were alive when Ya'akov came to Egypt, whether sons or grandsons, were the 'father's houses' to whom the land was divided... And it is written at the end [of the census in Bemidbar 26], "To these ['father's houses'] you shall divide the land, etc." According to the names of the 'father's houses' they shall divide. And so, the children of Yosef who were born afterward would be called in the name of their brothers and would be 'father's houses' , as it is written in Parshat Pinchas.

Accordingly, they would be incorporated under Ephraim and Menashe. As for the problem of a possible odd number of extra 'father's houses', one could speculate that Ephraim would receive one more than Menashe, based on Ya'akov's comments regarding Ephraim's superiority.

Answer 2

The Maharal in Gur Aryeh in his commentary to this posuk asks this question, in addition to asking why Yaakov bothered explaining this, being that Yosef did not have any more children afterwards. (Maharal explains why he feels that Yaakov knew that he wouldn't have more children.)

Maharal explains that Yaakov was actually disavowing Yosef of a possible misconception which might have inspired him to have more children. Seeing as to how his current children were made into Shevatim, Yosef might have thought to have a lot more children and they would all be Shevatim. Therefore, Yaakov told him that any future children would be subsumed in Ephraim and Menashe and would not be their own Shevatim. After understanding this, Yosef did not have any more children.

That being the case, there really was no plan that there would be more sons who would then need to be factored in. Yaakov was really saying "if you are thinking to have more kids..." and the whole thing was to disincentivize Yosef from thinking that he should have more children.

(Why Yosef would only have more children if they would be Shevatim the Maharal does not explain.)

He offers a second explanation in which Yaakov was really telling Yosef that he (Yosef) does not still have his own portion on top of Ephraim and Menashe, such that hypothetical other children would have their own independent inheritance.