According to Muslim Scholar Sheikh Ibn Al-Feasy Al-Hanbali, the Quran used "Sister of Aaron" and "Daughter of Amram" for several reasons. One of those is the "relative calling" or "laqb" that is always used in Arabic literature. Ahmad bin Muhammad bin Hanbal Abu 'Abd Allah al-Shaybani, for instance, is prevalently called "Ibn Hanbal" instead of "Ibn Mohammad". Or, Muhammad bin Idris asy-Syafi`i is always called "Imam Al-Shafi'i" instead of "Imam Idris" or "Imam Muhammad". This is how the Arabs refer to famous persons in their daily life. The same applies here; Sister of Aaron refers to "daughter of Aaron's siblings'", and daughter of Amram refers to "direct lineage of Amram" (Amram's descendants). This means that Mary was from the line of Amram, but not of Aaron's generation.