How does "The Hunt is On!" work if Kha'Zix and Rengar are on both teams?

The answer to this question does a good job of detailing how the "The Hunt is On!" secondary quest interaction between Kha'Zix and Rengar work. However, after seeing this interaction for the first time, and then later playing a blind pick game, I started wondering:

What happens if is more than one Kha'Zix / Rengar pair in the game?

This would only be possible in blind pick games, but you could potentially have Kha'Zix / Rengar vs Rengar / Kha'Zix. Does each pair get it's own secondary quest? Or is there just one secondary quest shared among all 4 champions?