1)
Why does the Pasuk add the word "l'Yaakov" by each of the sons born to Bilhah and Zilpah?
1.
Tosfos ha'Shalem (1), Ramban, Malbim, Ha'amek Davar: To teach us that although they were the sons of the maidservants, Yaakov considered them his children just like the sons of Rachel and Leah. 1
1
And the reason that it writes "l'Yaakov Ben Chamishi" and "Ben Shishi" by the birth of Yisachar and Zevulun (30:17,19) is because of the large number of sons that Leah bore, to teach us that Yaakov considered them all important (though it is not clear why we would have thought otherwise).
