math teaser, kinda tough

[lotus776]

The crew of a certain train consists of a brakeman, a conductor, an engineer, and a fireman, named in one order or another Art, John, Pete, and Tom.

John is older than Art
The brakeman has no relatives on the crew
The engineer and the fireman are brothers
John is Pete's nephew
The fireman is not the conductor's uncle, and the conductor is not the engineer's uncle.

which position does each man hold, and how are the men related?

good luck