"O sister of Aaron"

"O sister of Aaron! Thy father was not a man of evil, nor thy mother a woman unchaste!" (Surah 19:28)

Commentary :

Some Christian writers in their ignorance of Arabic language have accused the Quran of an historical anachronism inasmuch as it has spoken of Mary as “sister of Aaron”. Instead of regretting their own ignorance they seek to find fault with the Quran. The question of Mary having been called sister of Aaron in the Quran was put before the Holy Prophet himself and he asked the questioner if he did not know that the Israelites used to name their children after their Prophets and saints (Bayan vol. 6 p. 16. Jarir vol. 16, p.52). Mary has been here called the sister of Aaron and not the sister of Moses though both were brothers. For whereas Moses was the founder of the Jewish law, Aaron was the head of the Jewish priestly class (Enc. Bib. & Enc. Brit. Under “Aaron”) And Mary also belonged to the priestly order. Tabari has related and incident from the life of the Holy Prophet which gives an insight into the meanings of the Arabic words.s (ab) (amm) (ukht) etc. when safiyyah, the Holy Prophet’s wife. And incidentally a Jewess by descent. Once complained to the Holy prophet that some of his other wives had called her a Jewess in contempt, the Prophet told her to return the taunt by saying that Aaron was her father. Moses her uncle and Muhammed her husband. Now, the Holy Prophet certainly knew that Aaron was not Safiyyah’s father nor Moses her uncle. This tradition shows that the application of these Arabic words is by no means confined to the above-mentioned blood relations. Mary might have been called sister of Aaron by the way or reproach or taunt inasmuch as another Mary, the real sister of Aaron and Moses’s step-sister or his sister in law, had charged him (Moses) with having unlawfully married a woman (Numbers 12:1). A reference to this accusation is also to be found in the Quran in 33:69 (correction from original tafsir verse number).  Thus the elders of the Jews, by calling Jesus’s mother “sister of Aaron,” meant that as Mary the sister of Aaron had, by accusing Moses of unlawfully marrying a woman, committed a heinous crime, so did she. Like her namesake, commit a heinous act of giving birth to an illegitimate child.  (end of commentary )

Narrated Anas:

said: "It reached Safiyyah that Hafsah said: 'The daughter of a Jew' so she wept. Then the Prophet (ﷺ) entered upon her while she was crying, so he said: 'What makes you cry?' She said: 'Hafsah said to me that I am the daughter of a Jew.' So the Prophet (ﷺ) said: 'And you are the daughter of a Prophet, and your uncle is a Prophet, and you are married to a Prophet, so what is she boasting to you about?' Then he said: 'Fear Allah, O Hafsah.'" (Jami` at-Tirmidhi Vol. 1, Book 46, Hadith 3894)

Narrated Safiyyah bint Huyai:

"The Messenger of Allah (Peace be upon him) entered upon me and some words had reached me from Hafsah and 'Aishah. So I mentioned it to him. So he said: 'Why did you not say: "And how are you better than me, while my husband is Muhammad and my father is Harun, and my uncle is Musa?" That which had reached her, was that they had said: "We are more honored to the Messenger of Allah (Peace be upon him) than her," and that they said: "We are the wives of the Prophet (Peace be upon him) and his cousins." (Trimidhi 3892)

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From the first Hadith we read Prophet Muhammed Pbuh called his wife Safiyyah (May Allah be pleased with her) the daughter, niece and wife of Prophets. Though the second Hadith is daif we can see the correlation between the two. The first Hadith says Safiyyah (May Allah be pleased with her) was the daughter of a Prophet and niece of a Prophet and also married to a Prophet. Th second Hadith tells us who those Prophets were i.e. their names are given.  Here we can see that calling Safiyyah (May Allah be pleased with her) the daughter of a Prophet who lived long before her does not literally mean she was his actual daughter, rather she was a descendent from the line of the Prophets making her a daughter through linage.  

This is enough to prove calling an individual son, daughter or sister of a Prophet does not mean they were the real, biological child of that Prophet. This use of language was very common during ancient days by Arabs and Jews, and even now in some parts of the worlds such "epithet" is used whilst referring to someone.