Why did they report to Aharon?

The verse states that the spies came to Moshe, to Aharon, and afterward to the entire congregation. Why Aharon? He wasn't the one who sent them! Possibly, the spies wished to ensure that Moshe and Aharon, being brothers, would not be able to judge the matter as a Beis Din, since close relatives may not serve together as judges (see Choshen Mishpat 7:9). This may have been part of the spies' strategy to prevent a proper halachic investigation.