RaSh"I, commenting on [Bereshit 48:1][1], states:

> **ויאמר ליוסף**: אחד מן המגידים, והרי זה מקרא קצר. ויש אומרים אפרים היה רגיל לפני יעקב בתלמוד, וכשחלה יעקב בארץ גושן, הלך אפרים אצל אביו למצרים והגיד לו

> **That [someone] said to Joseph**: One of the tellers, and this is an elliptical verse. Some say, however, that Ephraim was accustomed to study with Jacob, and when Jacob became ill in the land of Goshen, Ephraim went to his father to Egypt to tell him.

The opinion of the "יש אומרים" answers the question of "who".

> **ויקח את שני בניו עמו**: כדי שיברכם יעקב לפני מותו

> **So he took his two sons with him**: so that Jacob should bless them before his death.

This answers the question of "why".

  [1]: http://chabad.org/8243#v=1&showrashi=true