Earlier in the week I read this article by Justine Larbalestier, where she talks about the importance of giving protagonists in YA novels proper relationships beyond a love interest - parents, siblings, friends, etc. Not only is it an interesting topic, but she praises the Uglies series by Scott Westerfeld, so she clearly knows what she's talking about. Nip over and read it, I'll wait.
I have a tendency to limit the number of relationships my main character has. I haven't written a lot of YA (though it's where I'm venturing now) but looking back at everything I've written of a substantial length (I'm talking at least 50,000 words), the parents are either dead or otherwise absent. There are a couple of exceptions, but they're missing more often than not. As for siblings, I have a tendency to bump them off as well. My protagonists are short on friends - sometimes by choice, sometimes by necessity, sometimes because they're just so damn unlikeable.
The thing is, I agree with Justine. These relationships are important, especially in YA, which features teenagers. They're getting to know themselves, and they discover that through their interactions and relationships with other people. With this in mind, I'm re-thinking the novel that I'm about to start writing. It's a YA novel, it features a teenage girl whose parents are alive but mostly absent. The story dictates that she be a bit of a loner, though, and I'm worrying about that. I'm thinking about creating a friend for her, probably a female friend, as all but one of the other characters are male.
Except, I'm concerned. These characters need to be in the story, the protagonist needs them, but you can't just throw together a character to fulfil a job. They need to be a character in their own right, and I don't want to make a hash of it. By keeping the number of characters down, you stand a better chance of making them all unique and interesting and engaging to a reader. I read a quote recently about how your reader should also want to read the stories of the minor characters (if someone knows the full quote and who I can attribute it to, let me know). Boosting the number of characters may help your main character, but it might also result in a bunch of cardboard cut-out characters who make your novel as dull as the back of a cereal box. It's a fine line to walk, but maybe a friend would help my main character. It's just hard to know what she's like when I've decided to create her rather than have her appear naturally.