GPIO pin current for LEDs

Hi, all
I am using arduino pro mini
If I connect single [ GPIO pin - LED - GND ], It will be very bright
So may intercept resistor to regulate brightness
My question is, if I connect bundles of [ GPIO pin - LED ]s to one [ resistor - GND ], will brightness of LED be constant? or changes as number of HIGH level GPIO?
The voltage should same -regardless of the number of HIGH level for LED- and I learned brightness of LED is depends on voltage. So I think all LED will get same brightness.
I want to regulate brightness but using less resistor.

LEDs need current control because when the semiconductor material gets warmer it conducts current better. More current creates more heat, allows more current ... until the LED gets destroyed. With metals it is the opposite, that is why incandescent light bulbs work without resistors.

The resistor limits the current that can flow through the LED.

Do not do that. If one LED is switched off the current trough the resistor drops and therefore the voltage across the resistor drops, increasing the voltage across the other LEDs. Resistors are cheap.

Select a resistor for the maximum brightness of the LED, use one resistor for each LED and then use PWM to dim them. You can use software PWM for LEDs if you do not have a hardware PWM available.

Thanks for answer!