Sometimes they're all three.
I have to send a quick shout-out to Sarah at Birds of a Writer, because I had absolutely no clue what to write about for today. Thankfully I decided to put out my feelers and she came up with this, and I thought it was a wonderful idea.
Parents are interesting creations, particularly in the world of YA fiction. Most of our main characters are so young that they're still minors, which means they're still under the legal guardianship of their parents. Considering the kinds of trials and adventures most of our teenage characters are forced to go through, they can't have their parents hovering over them every second telling them it's too dangerous, or worse: call the police and let them handle it instead of their underage children.
See, problem. Parents present problems, which means that the authors get to have to get pretty creative when they search for ways to get rid of them for part or even all of the plot. Because no parents means that the characters can basically do anything they want (within reason, of course).
Here are some common solutions for getting those pesky parents out of the way:
Dead parents are pretty common. What's more, their deaths could even have something to do with the plot. When I read Dracian Legacy, the main character's parents had died before the events of the novel, but later you find out that their murder is very much tied into the main events.
A danger of using dead parents? If you're placing your novel in modern times and your main character is under the age of eighteen, they need to have a guardian of some kind. Another family member, godparents, etc.
Neglectful parents. This category includes both the kind that are too busy with other things (like work or other family) or are too drunk/etc to notice their children. Or they hate their children and simply try to pay as little attention to them as possible. This category can apply to guardians, as well (since I already gave ya'll the warning about minors).
For example, in Cress, by Marissa Meyer, Cress is trapped on a satellite orbiting Earth. Her "guardian," Sybil, comes around once a month or so to take progress reports on her work as a spy and also bring provisions. Besides that? Cress is alone.
A perk of this is that you still have a parental figure of sorts, so you ca avoid any sticky legal stuff in regards to why the child has no parent. Because, technically, they do have a parent, That parent just doesn't pay much attention to their kid, which opens a world of possibilities.
Missing parents. Like the dead parents, parents that have disappeared can play an interesting role in the overall plot of the novel because it raises a lot more questions than the previous two. The main of these questions is: why did they leave? It can make way for a pretty tortured child. What's even funner is when those missing parents show up again during the course of the novel, such as in Marissa Meyer's Scarlet.
So those are three categories you can put those pesky parents into if you're having trouble working your way around them. There's other ways, of course. If you want them to be those caring parents who are around as much as possible, but they really interfere with some of the plot, another thing you can do is what Kate Karyus Quinn did in Another Little Piece: Anna's parents were in and out of the hospital, and at one point spent more than a few days there, with some medical issues that the mother was going through. Ergo: no parents around to keep an eagle eye on Anna, but at the same time they were those really awesome and nice parents who actually had an itnerest in their kid and cared about her.
Brainstorm. Trust me, it's actually kind of fun figuring out a way around the parents, and many of those ways can tie directly into the plot and create loads of conflict for you to work with.