How does the V-22 Osprey share engine power between its rotors?
It is possible to drive the two rotors of the V-22 Osprey from a single engine using a segmented driveshaft connecting both engine shafts via gearboxes:


The drive shaft is depicted in blue in the left wing. Source

Each engine drives its own rotor and the connecting shaft. If one fails the same rotation speed is maintained, but each rotor receives now half the power of the remaining engine.

A similar mechanism is also used on the CH-47 Chinook family:


Source

This is a CH-47 Chinook green drive shaft:


Source

On aircraft with two distant rotors, it is vital to have both rotating, as if one slows or stops the aircraft is unbalanced to the extend it crashes.