Answer:
Two people are born at the same moment, but they don't have the same birthdays. How could this be?
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.
It cannot be seen, it weighs nothing, but when put into a barrel, it makes it lighter.
I have three hundred cattle, with a single nose cord
I fly through the air on small feathered wings, seeking out life and destroying all things.
I am black within and red without; with four corners round about. What am I?