Can I steal a neutral wire from another circuit?
The other answer and the comments are of course correct, but there is a second aspect to it: it won't work.

Actually, it may appear to work, until you try to install a GFCI just about anywhere on either of the two circuits involved.

A GFCI works by comparing the current through the hot wire and the corresponding neutral wire. If those two currents don't match, the GFCI will trip. When you "steal" the neutral from another circuit, the current will go out through one hot wire, but come back through a different neutral.

I actually had an older home where the dishwasher and some kitchen outlet were wired on two different circuits with a shared neutral (that was probably grandfathered in from an earlier era). Trying to bring the kitchen up to code, I was going crazy trying to figure out why the GFCI would trip every time I turned on the dishwasher!