No, one Arduino can comfortably control several steppers. The typical 3D printer uses 4 motors and one Arduino.
Your code at the moment does something like
Move StepperOne 200 units
Move StepperTwo 100 units
What you need is something more like
Repeat 200 times:
Move StepperOne one unit
Has StepperOne moved an even number of times?
Yes - Move StepperTwo one unit
So yes, the program suddenly becomes more complicated. In my example above I have assumed a fixed ratio (2-to-1). You can have any ration (a rational fraction to be mathematical correct) with a bit of integer math to decied if the slower stepper needs to move a step.