I've created a loop of 8,000 while I am going to assume is 8 seconds. Every eight second I want the two leds to blink.
Lousy assumption. There is a function, millis(), that will return the number of milliseconds the Arduino has been running. Record when the LEDs last were flashed. When the difference between "now" and "then" is greater to or equal 8000, flash the LEDs again.
if (brightness == 0 || brightness == 100)
The maximum brightness is STILL not 100. It is 255.
Use the Tools + Auto Format option to properly indent your code. Python performs actions based on the level of indenting. C++ does not. Indenting is for humans. The reason for using proper indenting is so that YOU can follow the code.
You will be able to see that your else clause goes with the wrong if statement.
You have two things that you want the Arduino to do. Separate the two actions.
You want one LED to fade from off to on, and back again. There are a certain number of steps required to make this happen. Determine what that number of steps is. It is NOT 200.
Given the number of steps, and the total time (if that is relevant) you can determine the time that the LED should remain at each level.
Keep in mind that the human eye can not perceive the difference in brightness of an LED when analogWrite(pin, 137) and analogWrite(pin, 138) are executed. So, you may want to make the increment a bit larger. Steps of 5 are generally discernible. This will, of course, affect the number of steps, and the time that each steps is to remain in effect.
Once you know how long the step is to last, follow the blink without delay example to fade without delay IGNORING THE NEED TO BLINK THE OTHER LED(s).
When you get that working, it is easy to add the code to make the other action (blinking the other LED(s) every 8 seconds). happen without affecting the fading action.