Why does it list Amram and his wife, and not just write 'Mishpachas ha'Amrami'?
Ramban: Because his children were divided into two sections, Kohanim and Levi'im, and it is befitting to list Aharon and his sons independently.
And why does it add "asher Yaldah osah le'Levi be'Mitzrayim"?
Rashi: To teach us that Yocheved was born in Egypt
Ramban: Hashem held her back from giving birth earlier, because (she gave birth to the redeemers