Vayechi 1 - Yosef's Other Sons

Bereishis 48:5-6:
ועתה שני בניך הנולדים לך בארץ מצרים עד באי אליך מצרימה לי הם אפרים ומנשה כראובן ושמעון יהיו לי. ומולדתך אשר הולדת אחריהם לך יהיו על שם אחיהם יקראו בנחלתם

"And now, your two sons who were born to you in the land of Egypt until I came to you to Egypt are mine; Ephraim and Menashe are like Reuven and Shim'on to me. But your offspring that you bore after them should be yours; upon the name of their brothers they shall be called for their inheritance."

This verse strongly implies that Yosef had other sons besides the two that we know about, despite there being no mention of them within Tanach or divrei Chazal.

R' Yehuda Herzl Henkin, in Shu"T Bnei Vanim 4, ma'amar 19, notes this curiosity. Based on Devarim 25:6 (the parsha of Yibbum), he suggests that על שם, upon the name of, refers to one person replacing another in the context of an inheritance, and thus Ya'akov was instructing Yosef that Ephraim and Menashe have a share in Ya'akov's possessions with their uncles, while their younger brothers would inherit their shares of Yosef's possessions. Ya'akov's possessions were primarily in movable objects that he had brought down to Egypt, while Yosef, who had risen to power in Egypt, also had significant real estate holdings. R' Henkin suggests that Ya'akov made this strange stipulation in order to ensure that Ephraim and Menashe's descendants would not hesitate to leave Egypt at the Exodus because of their land holdings; Yosef's other children, on the other hand, assimilated into Egyptian society, and did not leave Egypt.

He makes three suggestions regarding why Ya'akov felt that Ephraim and Menashe would be less likely to assimilate into Egyptian society than their younger brothers, so that this stipulation would strengthen a positive trend rather than fruitlessly opposing a negative one:

1) Yosef had to take more precautions in the upbringing of his elder sons because of the lack of other suitable role models, which was not the case by Yosef's younger sons. However, the younger sons still assimilated because of their residence in the capital of Egypt, rather than in Goshen where they would be in close contact with these role models.

2) When Ephraim and Menashe were born, Yosef felt like a foreigner within Egypt (as shown by the names that he gave them), and he passed on this feeling of alienation to his elder sons, but once his family came, he felt more comfortable in the land.

3) Yosef's experiences in revealing himself to his brothers and seeing his father for the first time in twenty-two years left a mark on his elder sons, who witnessed these events, thereby giving them a greater heartfelt connection to the family.