Word of Dante: The interpretation that Sarastro is Pamina's father is fairly widespread and shows up in many stagings of the opera, particularly when the libretto is translated and the connection can be made more explicit, and so is frequently taken for granted. (In fact, the interpretation only works because the Queen of the Night's lines about Pamina's father are nearly always cut for time.)
Alternately, he was based on Mozart's friend Emanuel Schikaneder, whom Mozart personally described almost word for word as Papageno is normally played... and who originated the part on stage.
And the role of The Queen was originally played by Mozart's sister-in-law Josepha Weber, who, according to Mozart, was a cold and unpleasant person and only needed to "play herself".
In Amadeus there's a memorable scene in which Mozart's mother-in-law-from-Hell is telling him off and in the midst of her tirade she turns into the Queen of the Night.
In a more musical example, Sarastro's vocal lines are quite simple, making the role accessible to a larger number of deep-voiced men, who are something of a minority to begin with. (It isn't known if Mozart wrote this way because all he had to hand was a bumbling James Earl Jones, but production managers have been thanking him ever since.)