Is there any equivalent function in C to the system call "Fork" in Unix?
That would be an interrupt
I want to have parallel control in more than one motor.
Iwould be very wary of driving more than one motor with the same uC, how will it handle keeping one timed correctly while handling exceptions (stall, overcurrent etc) in the other.
I believe you can fit what you need into a LPC920 which will cost you about $1.50 so why worry about fitting more than one motor into one chip.

Erik