It is mentioned in your Qur'an that Mary was the sister of Aaron (pbuh) ?
1. In the semitic languages sister also means descendant The qur'an mentions in surah maryam, chapter 19 verses 27-28
"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!'"
Christian missionaries say that prophet muhammad (pbuh) did not know the difference between mary the mother of jesus (pbuh) and miriam the sister of aaron (pbuh). The time span between both was more than a thousand years.
In the arabic construction of the sentence, sister is also considered as a descendant. Thus, when the people said to mary, ukhta haroon i.e. 'sister of aaron' it actually means descendant of aaron (pbuh).
2. Son also means descendant It is mentioned in the gospel of mathew, chapter 1 verse 1 "jesus christ, the son of david,....".[mathew 1:1]
gospel of luke chapter 3, verse 23 "and jesus himself began to be about thirty years of age, being (as was supposed) the son of joseph, ....."[luke 3:23]
Did jesus (pbuh) have two fathers? What do you call a person who has two fathers? The explanation of the phrase that jesus (pbuh) was the son of david (pbuh), is that jesus (pbuh) was a descendant of david (pbuh). 'son', here means a descendant.