According to Exodus 7, Aaron was three years older than Moses when they spoke to Pharaoh.
The chapter gives their ages directly: Moses was 80 years old and Aaron was 83 when they confronted Pharaoh. The age difference is therefore three years. Aaron’s role was especially prominent because he served as Moses’ spokesman, while Moses was the leader who received God’s instructions.
Aaron was Moses’ older brother and also the brother of Miriam. In the Exodus narrative, he performs signs with Moses’ staff and speaks before Pharaoh because Moses says he is slow of speech. Later biblical books identify Aaron as the first high priest of Israel.
Readers sometimes remember Aaron mainly from the golden calf episode or the priesthood and overlook this numerical detail near the beginning of the plague narrative. The figures belong to the biblical chronology itself; they are not estimates reconstructed from Egyptian records.