Exodus 28:2-8

Aaron : a son of Amram; brother of Moses,son of Amram (Kohath Levi); patriarch of Israel's priests,the clan or priestly line founded by Aaron

Leviticus 8:7-8

Thummim : a system (or device) to obtain divine guidance (IBD)

Urim : a device to discern divine guidance, used with the "Thummim"