In this week's Parsha, Yaakov passes away. Before he passes away he gives all of his sons Brachot, and then blesses his grandchildren, Ephraim and Menashe. But why did Yaakov bless only Yosef's children and not his other grandchildren?
One explanation is that they were treated as part of the twelve Shevatim because they were given a plot of land when they entered Eretz Yisrael. Yaakov treated Yosef as the B'chor, or firstborn, and thus got a double portion of land in Eretz Yisrael.
The Midrash explains that Yaakov was supposed to have fourteen children. Due to the fact that Reuven moved the bed of Yaakov into the tent of Leah instead of Yaakov's midwife Bilhah, two children remained unborn to Yaakov. This caused Ephraim and Menashe to be like the rest of the Shevatim.
A final opinion says that because Menashe and Ephraim preserved their connection to their forefathers despite living among one of the most disgusting nations of the time, they were given the Zechut to be blessed by Yaakov. May we all follow in the footsteps of Ephraim and Menashe and live as Bnai Torah, preserving the teachings of our forefathers.