Jethro
See Exodus 18.
I've long puzzled over Jethro's role in Exodus, and I think I'm making some progress at last.
Jethro features in Exodus 2 (as Reuel, where he welcomes Moses the refugee), in Exodus 4 (where he sends Moses back to Pharaoh in peace, although Moses hasn't been strictly honest about the nature of his mission), and in most detail in Exodus 18.