In terms of "relationship," I would look at this more as to how they got along rather than how they were "related." There seems to be no connection in terms of Zeus being Prometheus' father, etc. (though it would seem that Zeus really got around).
The connection is more that Prometheus gave humans fire (stealing it from Zeus) because he felt sorry for them. This way they could have light after dark, be warm and cook their food. However, it was seen as an affront to the gods, for once mankind had fire, they were less dependent upon the gods...perhaps even more god-like themselves...or so the story goes.
And so Prometheus was punished, chained to a...
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