Who are the "Kehal Amim" to whom Ya'akov is referring?
Rashi: A Pasuk above (refer to 35:11:3:1), discusses Hashem's promise to Ya'akov that (besides "Goy", which referred to Binyamin, who was yet to be born), one of his sons would be divided into two - a privilege that he now bestowed upon Yosef.
What are the ramifications of the division of Yosef into two tribes, who would be reckoned like Ya'akov's own sons?
Rashi (in Pasuk 5): That they would take two portions in Eretz Yisrael. 1
Ramban and Rashbam: They actually received double portions, like Reuven and Shimon. 2
They did not receive extra in Eretz Yisrael, since the land was divided according to the individuals, and not according to the tribes. How are they considered two? Each has its own Nasi, each has a separate lot in the lottery to divide Eretz Yisrael, and each has its own Degel (place in the encampment in the Midbar - Rashi on Pasuk 6. See Ramban's strong objection to this explanation. Riva says that Rashi means like the Rashbam, that each tribe received an equal share, within each Shevet all received equally. (If so, why did Rashi need to find other consequences of being considered two?!) (PF)
Because the land was distributed according to the tribes. See also Ba'al ha'Turim.