Weighted Distribution

Fairness is a strange subject to consider. Suppose your story has five main characters in it. should they all get an equal amount of screen time? If they're all equally important, it would make the most sense. It's certainly the fairest way to handleit.

But what if one of those characters is comic relief? What if one of those characters is a brutish mute? What if one of those characters bears the mark of legend and must overcome their personal beliefs to fulfill the prophesy that has guided his life? Should all of these characters have the same number of pages spent describing them?

There isn't a right answer. This isn't a rhetorical question. You need to find the answer for you. Most people will find that a weighted distribution is the best way to go, giving the characters with the most importance the most amount of time. But if you give the same amount of time to all your main characters, you may find yourself discovering that an ancillary character is actually pretty interesting and more important than you expected (though it's not always a guarantee that you'll find that).

For me the answer is usually based on the action. Whoever is doing the most stuff gets the most screen time. But that's me and I like direct storytelling. You may have a character do a lot of things off-screen because it allows you to do a big reveal later, or because you just don't think it's relevant to the plot. You may also find yourself focusing entirely on one character (which I also like to do sometimes), or simply never having your party split up.

This is why you need to answer the question. Most any distribution will work fine, but it's up to you to figure out which one produces the effect you're looking for.