Control two stepper motors simulatenously?
You likely have other issues to boot based on what you said about only X1 moving, but first I suggest resolving the bug in your code.  It appears to be that you have delays between your digital writes to x1, x2. And set their directions to the same.

At the very least you should be writing to X2 step every time you write to X1 step.  If your wiring is identical and the motors are essentially attached mirrored on opposite sides of a shaft, don't forget to set the directions opposite before you start sending steps. (If they are on opposite sides of the shaft, one spinning counterclockwise means the other spins clockwise.  You can also play wiring tricks with what coil goes where and how, but identical is simpler.)

digitalWrite(X1dir,HIGH);
digitalWrite(X2dir,LOW);


Or 

digitalWrite(X1dir,LOW);
digitalWrite(X2dir,HIGH);


Then step it like

digitalWrite(X1step,HIGH);
digitalWrite(X2step,HIGH);

delayMicroseconds(2000);

digitalWrite(X1step,LOW);
digitalWrite(X2step,LOW);

delayMicroseconds(2000);
...