Upvote:18
They are transliterated from two different languages: Hebrew and Greek.
The transliterations make sense when compared to the original pronunciations.
Of course Mary and Jesus must actually have had Hebrew/Aramaic names instead of Greek ones. Quite probably their names actually were מִרְיָם and יְהוֹשֻׁעַ. However, they still are only mentioned with the Greek translated versions, so by transliterating from Μαρία and Ἰησοῦς the translators are keeping closest to the original.