Sometimes they are the actual offspring of the lead (such as in the Charlie Madigan series by Kelly Gay), they belong to another important side character (Tink's brood in Harrison's Rachel Morgan series), the niece/nephew (Nancy Holzner's Deadtown), or the stray kid/teen befriended by the lead (Ilona Andrews' Kate Daniels series, for example). Sometimes they are annoying (as kids can be), a challenge, but they do have their place.
Here are a few of my favorites - kid sidekicks who have earned their spot among the other, more grown-up sidekicks.
Over the course of this series, we've encountered not one, but three notable kid/teen sidekicks.
Derek - Kate's original "teen wolf sidekick", Derek has come a long way from the cocky teen trying to intimidate Kate at her introduction to the Pack in Magic Bites. Derek could handle himself in a fight - a good thing since trouble sticks to Kate like glue, but he still had a lot to learn about his own limitations (something he knows too well now). He was Kate's first real tie to the Pack (I don't count Jim since she mainly knew him as a merc), and the first person in a long time that she felt responsible for. Which leads us to...
Julie - A near homeless waif who picked the wrong boyfriend and whose mother has gone missing, Julie first appears in Magic Burns. Julie is more kidnap/calamity prone than the other sidekicks because, well, she's 12 when we first meet her and while she has her own very important magic power, she is not a fighter. Yet. She is crucial in bringing out Kate's maternal/"crazy aunt" side, and is also a very important component of the Kate-Curran relationship (that scene at the Keep before they go off to rescue Julie - yep, you know what I'm talking about!). I also like how Julie has been through a lot of hellish experiences but she still keeps going. She is a fighter and has a resourcefulness about her. I think it will be very interesting to see her all growed up.
Ascanio - The newest teen sidekick (first appearing in Magic Slays), this one is a Bouda (that's were-hyena) with some authority issues. He's 10 times more horny than your normal teen boy and he's a deadly fighter. And now he's Kate's responsibility too. We're still learning about Ascanio, but he's already had some very good scenes and I can't wait to see his and Andrea's interactions in the next book.
Edge series by Ilona Andrews
Family is very important, with a very young Georgie and Jack playing a key role in On the Edge and Lark and Gaston in Bayou Moon, but for me, the kid/teen sidekicks Gaston, Jack & George really come into their own in Fate's Edge. Gaston has had to deal with being cast out by his father, starting a new life with William and training to be a Mirror agent. Jack is finding life in the Weird very difficult to adjust to, and is constantly worried he will be sent away. George is coming into his own power, tries to protect his brother, and under it all is tired of all of the Weird snobbery. They've all had to grow up fast, although they still have a lot to learn.
Under Witch Moon by Maria E. Schneider
Lynx from Schneider's witchy series is one of my favorites. Adriel, our heroine, feeds him and tries to get get close enough to help without scaring him off for good. Adriel is a loner, but that starts to change in this series starter, and Lynx is a big part of that change. Too young to be on his own, too proud to admit it, skitterish and usually on the wrong side of the law, Lynx is a prickly character, but one I was pulling for the whole time. He's also got claws, so he can take care of himself. He's a good ally to have, even if he wouldn't want to admit it. I've heard that he'll be in the next book as well. Under Witch Aura comes out Nov/Dec 2011.
Darkness Becomes Her by Kelly Keaton
OK - I admit it, this is a YA UF (although I would rank it with the more adult-ish YA UF series out there), but Violet is such an awesome character that she needs to be here. Violet belongs to a ragtag bunch of kids living in New 2 - the paranormal haven that is the rebuilt New Orleans. I can't even tell you what Violet is, to be honest. She appears very young (tweens?), goes around in a black gown, wears masks, has a pet alligator, and she has teeth. Sharp ones. But she is also one of the most loyal friends Ari finds and is an integral part of Ari making a home for herself in this strange place.
So there's some of my favorites. What about yours?