1)
What is the Chidush that Efrayim mourned over his sons' death?
1.
Malbim: It teaches that he was alive at the time.
2)
Did Efrayim have more than one brother?
1.
Ramban (Bereishis 48:15): (Yes! 1 ) Since a Navi (Yakov) told Yosef 'sons born to you after them will be called on the name of their brothers', surely Yosef fathered more sons.
2.
Radak: "Echav" refers to his relatives and confidants.
3.
Malbim: "Echav" refers to Shuselach's brothers.
1
Ramban did not address this question. He merely asserts that Yosef had more sons; perhaps they died before this episode. (PF)
