Answer:
A serpent swam in a silver urn, A golden bird did in its mouth abide, The serpent drank the water, this in turn, Killed the serpent. Then the gold bird died.
My first is a creature whose breeding is unclear. My second, a price you must pay. My whole can be found in the river of Time and refers to events of today.
A harvest sown and reaped on the same day In an unplowed field, Which increases without growing, Remains whole though it is eaten Within and without, Is useless and yet The staple of nations.
The itsy bitsy teeny weeny yellow polka dot variety is quite popular.
Put into a pit, locked beneath a grate, guarded through the night, yet it still goes out.
I am your mother's brother's only brother in law. Who am I?