Question: Mary addressed as Sister of Aaron(P) is a contradiction. Below is the verse:
At length she brought the (babe) to her people, carrying him (in her arms). They said: "O Mary! truly an amazing thing hast thou brought! "O sister of Aaron! Thy father was not a man of evil, nor thy mother a woman unchaste!" [Qur'an 19:27-28]
Answer: It turns out that Christians in Najran during the time of the Prophet(P) raised a similar objection and it was answered by the Prophet(P). In Sahih Muslim, the hadith related by Mughirah ibn Shu`bah  says:
When I came to Najran, they (the Christians of Najran) asked me: You read "O sister of Harun" (i.e. Maryam) in the Qur'an, whereas Moses was born much before Jesus. When I came back to Allah's Messenger(P) I asked him about that, whereupon he said: The (people of the old age) used to give names (to their persons) after the names of Apostle and pious persons who had gone before them.
In the Bible, Elizabeth was called daughters of Aaron(P). Was she literally a daughter of Aaron?
In the days of Herod, King of Judea, there was a priest named Zechari'ah, of the division of Abi'jah; and he had a wife of the daughters of Aaron, and her name was Elizabeth. [Luke 1:5, RSV]
Or Jesus(P) was addressed as Son of David in the Bible. Was he literally Son of David(P)?
And the crowds that went before him and that followed him shouted, "Hosanna to the Son of David! Blessed is he who comes in the name of the Lord! Hosanna in the highest!" [Matthew 21:9 RSV]
But when the chief priests and the scribes saw the wonderful things that he did, and the children crying out in the temple, "Hosanna to the Son of David!" they were indignant; [Matthew 21:15 RSV]
If we take that literally then it is also a contradiction in the Bible.
Modified From Islamic Awarness.