I don't own the Secret Saturdays. I don't own Doyle.
I own Corbin, Zander, the servants, and whoever else manages to make an appearance.

Corbin and Zander eventually learn Doyle's name, but until then, he's still "the boy" or "the child." (And maybe "the younger boy/child" when he shares a paragraph or ten with Zander.) Even in scenes written from his perspective.
Hmm, wonder if I should change some of the previous chapters accordingly. Say, all of the "Stray" chapters up until this point? Yes? No?
I'm pretty sure I never refer to Zander by either of those labels—though he may sometimes be "the older boy/child" when sharing text with Doyle.

Icestar (chapter 20): No, I don't mind you asking. I hope you and other readers don't mind that I'll take my time to answer; you've provided me with an opportunity to lay out more details for any curious readers.
Much of the story has been edited since I first set a reply (thanks to "And Your Enemies Closer"), so the actual reply has also been edited. The answer is still a little involved, but hopefully not as much as the original version.

It goes without saying (yet I'll say it anyway; I'm ornery like that) that Doyle's actual age depends on the Word of God.
Also, my ages are based on calendar year rather than any question of when his birthday might really be. The date has yet to be relevant for my purposes, so unless JS ever mentions it, I'm just not going to bother.
For the purpose of my timeline, I—who have no grasp of judging age—guesstimated him at about 5 years old, and Drew as 10, when their parents died. I still say I can drop his age by a year or two without hurting my timeline, though too much would mean more hand waving regarding his survival skills.
Then comes the Child's Plight arc, the bulk of which took place the year later, making Doyle about six. (New Job—in which Doyle did not participate—starts the same year Doyle's parents died, and ends the same year Child's Plight begins.)
The Stray arc (the one to which you replied) started a full year after the Child's Plight arc ended (you may recall that the first three lines of Chapter 15 specifically mentioned this), making him at least seven. However, a good chunk of winter passed between then and now, and I don't know what month his birthday is; I don't know if he's still seven, or if he's already eight, by the time your review came up.
By the time we get much further into the Stray arc, though, say by chapter 26 (probably late summer, or into the fall), we can safely assume that he's at least eight.
Then for future arcs: The Hunted may technically begin the year he's eight, and Corrections might bleed into the year he's ten, depending on month in either case, but a chunk of both of them take place while he's nine.
After...the next arc he appears in is as an adult (Drew gets more screen time in the meantime), and I pretty much stop caring about his age, outside of remembering the duration of the story.
Again, I have no grasp of judging age, and while I'll hand-wave a lot of the things by using the "need to survive is an effective teacher" routine (which I'll probably use in future dialogue), it may be that some of his survival skills are...unrealistic for his age, even with that excuse.
In addition, some of my chapters make specific reference to the passage of time, so I'll need to remember what I'm doing, lest I start messing up my own timeline.

Okay, so that still managed to be rather involved.
*shrug*
Oh, well.

Stray

When Corbin returned in the morning to feed the animals, he found the child curled up against that stallion. When he tried to approach the stables, both of them came wide awake.

Viper watched Corbin warily, but eventually relaxed his stance and nudged the child out towards the man.

To Corbin's relief, the child went where the animal directed. To Corbin's astonishment, the animal fixed him with a very familiar glare.

Corbin shivered. Viper only gave that look when someone took out one of the foals Corbin sometimes boarded. More than one had returned from the stables with broken ribs, if the foal was even scratched up from thorns.

But Viper had never looked that way at Corbin before.

The question was, was that good for the child, or bad? Corbin had no idea why Viper had turned gentle with the boy, and didn't want the child to count on that behavior if the stallion should change his mind again. Not to mention how difficult it made any effort on Corbin's part to help the child if the stallion's behavior should continue....

Time enough to figure that out later, he scolded himself. Be glad Viper let me take him now.

Corbin showed the child where to relieve himself and clean up, found a slightly overlarge change of clothes for him, and directed the servants to bring breakfast up to Zander's room. The meal was plain oatmeal, with a dish of mixed nuts.

Corbin wrestled with the nutcracker for a few minutes before the child took the dish and shelled a few of them by hand. Corbin deliberately ignored the feat, though Zander watched in amazement, too stunned to manage more than a quick thank you as he accepted the pieces.

"Where'd you learn that," Zander finally managed after his third nut, "from squirrels or something?"

"Yeah," the child said. "They taught me how to get the shell off without losing...most...of...." Corbin and Zander stared at him, and the boy trailed off; their expressions reminded him uncomfortably of how the farmers looked at him when he talked to their animals. "Um," he mumbled, "something like that." He used the nutcracker after that.

Corbin watched the child examine the food. The boy picked at the oatmeal—Corbin had made sure the boy saw him serving all of them from the same pan—but he didn't show any hesitation over the nuts. After Corbin and Zander waved off more helpings, the child set to work finishing the bowl off.

Corbin waited until the child was finished before talking about the "job."

"Job?" Zander raised one eyebrow. "He's here for a job?"

"Benton...had a good idea for suggesting it," Corbin replied, attempting to conceal a grimace. The child might misinterpret if he realized Corbin disliked the notion of putting him to work.

Zander glanced at his father's guarded expression, shrugged, and went back to his meal. He took the role of observer, participating in the conversation only when addressed, and watched the child's reactions so he could compare notes with his father or Benton later.

Like your mother, Corbin mused, taking note of Zander's change in attitude and saddened by the reminder. We've taught you too well. He shook himself out of his memories and focused on the child in front of him.

"I suppose the first thing we need is introductions," Corbin said. "The man that brought you here is my friend, Benton. My name, as I think Benton told you, is Corbin Revan. Zander, there, is my son." The child nodded at each name, and repeated them when prompted. "What do we call you?" The child hesitated, and Corbin allowed a smile on his face. "I can't very well call you 'boy' when I want your attention, can I?"

The child appeared to think about this, and shook his head. He frowned, and took several minutes before he tried to answer. He finally just shook his head again. "I can't. I...I don't remember."

"Well, that's all right," Corbin said. "Nothing to be ashamed of." He was not surprised that the boy had forgotten his own name. Many beggar children didn't know theirs to begin with.

"You'll remember soon enough," Zander said. "If you like, we can figure out something to call you until then."

"So, exactly what did Benton tell you about your...job?" Corbin tried to suppress the note of distaste at the last word. He only hoped the child didn't notice...or misinterpret.

The child gathered his thoughts, and slowly repeated his conversation with the hunter.

When he was done, a few moments of silence passed while Corbin thought about what to say. "All right," he said with a sigh. "So what do you think, Zander? Sounds to me like Benton wanted him to work for you. What do you want him to do?"

Zander shrugged. "Easy enough. Stick around, let me talk at him once in a while, share my lessons, things like that. Do a lot of the things I like to do, so's I've got someone to do them with." He wanted to tell the younger boy that he just wanted a friend, but given what Benton had told them....

"That's...that's all? Just...stay near you?" The child frowned. "But...there's a village real close. If that's all you want me for, wouldn't it have been easier—"

Zander and Corbin shook their heads. "I get bored," Zander said, "being stuck here without nobody near my age to talk to. I mean, I like having you around, dad," he added with a sardonic grin, "but you're a grown-up. I gotta have a kid around."

Corbin suppressed the urge to snort. "As for the village, a lot of those kids only try making friends with Zander because their parents wanted something from me." It pained him to remember that the younger boy would understand that only too well.

"None of them cared two ways about me," Zander added bitterly. "And they ain't tried that in years, not since we kicked the last one out."

Corbin nodded. "We have...very little patience for that sort; most of them don't even make it past the servants." He fixed the child with a hard look. "Please understand. We don't expect to have you spend a few minutes, or a few days, or such, with Zander, and then send you on your way. My son's been sick most of his life. Sometimes he gets better, sometimes he gets worse, but he's been confined to his room most of that time. To the house, all the time. You being here may be the only chance he has at having a 'normal' childhood." And maybe the best chance you'll get, Corbin thought. "I expect you to live with us, for however many years we need."

The child blinked at the word "years."

Zander nodded at younger boy's surprise. "If I wanted a servant, dad's got plenty to pick from. But I feel like I got to pretend to be an adult around them. I need a companion, someone I can try to be a kid with. Look, Benton said he thought you might be able to make me better, right?" The younger boy nodded slowly. "Well, that's going to take time. A long time." Zander shrugged. "If you don't want to, you don't have to stick around. But me and dad would like you to give it a try, all right?"

"I can't," the child said. "Not the whole time. I'd need...I'd need time to hunt—"

Corbin shook his head. "If you want to hunt, that's fine. But I can and will feed you, no problem. If you stick around long enough, you'll need other things to get the job done, too. I'll provide clothing, any tools you think you need. Like for those carvings Benton mentioned; if you want to make those, you go right ahead. I'll supply all the wood you need." He smiled. "If you need anything, you need only to ask."

—

Every night for a month, the child returned to sleep in the stables, though Corbin and Zander eventually convinced him to stay in the house now and again.

He stayed with Zander when the older boy received his meals and lessons. When Benton visited, the child followed him for other lessons that the hunter insisted he needed. He accompanied Corbin every day for yet more lessons, to learn how the man tended to his animals, and Corbin gradually revealed the circumstances in which he acquired each one. The only one Corbin refused to explain was Viper, though he thought the boy might understand the stallion better than anyone.

The younger boy made many wood carvings for Zander, and he often watched Zander playing with the wood pieces, making up stories about the animals and the places they might live. Zander coaxed the younger boy into making suggestions and occasionally participating in these games.

As time passed, he improved at making those carvings, but Zander's favorite piece was the first the child had given him: a rough shape of Viper that the older boy had taken to wrapping himself around while he slept.

Dr. Perez made several visits, and declared that both children had vastly improved, though he continued to fret over the younger boy's emotional health.

When the servants traveled into the village for supplies, Corbin occasionally sent the child with them. He explained that he wanted the villagers to understand that the child was under his care, now, and that interfering with the child meant interfering with Corbin. Sometimes Benton took him to sell meat to the villagers.

Few enough villagers paid attention to the child when he was with the servants or Benton. Most of those who did, did not want to alienate Corbin or the hunter, so they kept their opinions to themselves.

In all this time, Corbin spent his time researching two problems: finding out exactly where the child had come from, and how to officially adopt him into the family. Benton and the household knew he was looking into the first, and helped where they could; he spoke of the second only to Zander, who had first suggested it.

Several months passed in this manner, without incident.

What's wrong with Zander? I'm not sure. I just know that he and his mother had gotten sick when he was very young, and his mother died of whatever it was. Was it an actual (but not very contagious) sickness that Zander and his mother both had the misfortune to catch? Or is the "sickness" a symptom of something else entirely?
And whether sickness or symptom, was it misfortune or malice?
Whatever it was, it ran its course quickly enough and left nothing in its victims of the original cause (nothing that the doctor could identify well enough to treat, at any rate), though the damage (namely the continued drain of his strength) is permanent.
I've got a few speculations bouncing around in my skull, but so far, they should all be in the background. They may come up as vague hints (if they ever stop bouncing around long enough for me to pick one), like some of my other "before the avalanche" ideas do, but none of them should impact the story at large.
Suggestions?