No, If the RPM rating of the motors is different then the motors will turn at different speeds.
Example:
Motor 1 has a base frequency of 60Hz and a RPM rating of 1775. This means that when 60Hz is supplied to the motor, the shaft will turn at a rate of 1775 revolutions per minute.
Motor 2 has a base frequency of 60Hz. and an RPM rating of 1780. This means that when 60Hz is supplied to the motor, the shaft will turn at a rate of 1780 revolutions per minute.
This ratio will hold true regardless of the frequency applied to the motor. If 30Hz is applied, then motor 1 will turn at 887.5 RPM and motor 2 will turn at 890 RPM.
In order for multiple motors to run at the same speed from a single VFD, the RPM rating of all motors must be the same. It is best if all motors are identical so that not only the RPM rating is the same, but also the horsepower and full load amp rating.