HOW DID AARON SURVIVE THE KILLING OF THE HEBREW BABIES?

Exodus 1:22. Then Pharaoh commanded all his people, "Every son that is born to the Hebrews you shall cast into the Nile, but you shall let every daughter live."

Note: The assumption of contradiction is that Moses was later revealed to have a brother named Aaron who his three years older than him.  So how did Aaron survive the slaughter of the infants? First of all, it's very likely that the law came into effect right around the time of Moses' birth, so Aaron would have already been 2 or 3, and thus no longer a baby.  And on the off chance that the law WAS in effect when Aaron was a baby, Exodus 1:17-20 mentions that many Hebrew babies were saved from the the Pharoah with the help of midwives, so it would still be possible that Aaron would have survived.