If they are humans . . .

I was wondering that too. The flashback sequence from the 1st season shows them as small children being taught in his underground lab. This implies that they've been with him since birth or shortly thereafter.

So, are they his kids or someone elses? If they're his, who was the mother? If they're not his, how did he come to be their adopted father? Are they orphans and if so, how did they come to live with him? Who are their real parents and what happened to them?

The bionic kids refer to him as "Mr. Davenport" not as Dad or Father or Step Father etc... implying they don't see him as their father either.

It's pretty disturbing to think that he cloned them simply for experimentation or grew them in a lab, it is a kids show after all. Or adopted them for the same purpose. On the other hand, no explanation has been forthcoming from the writers leaving us all to speculate.

It may be something they're going to explore in future episodes or something they'd rather we all don't think about. And come to think of it, maybe we're all thinking too much about it anyway.

It is after all, "just a kids show."

I think the writers were very careful not to make them Davenport's bioligical children for the simple fact no (loving) father would ever experiment on his own children, let alone put them in harms way the way they are expected to perform under on their missions.

By having them be "Lab Rats", this allows an emotional detachment that might get in the way of either of them doing their duty. It also addresses any concerns parents groups, or older viewers might have as well.

However, it's obvious he cares about them because in the time travel episode with Future Leo, it's the fact he lost them that prompts him to spend the next seven years trying to crack time travel to prevent what happened at the Super Collider. Also, in Concert in a Can, Brie calls him Dad, and says she wants to spend time with him like the other fathers do with their kids. I don't know if that was a slip up on the writers part, or if they are slowly hinting at things to come in S2?

The hour-long season 2 finale really didn’t explain as much as I’d hoped.

***Spoiler Alert***

Davenport’s brother “Douglas” turns out to be the mysterious stranger who’s been spying on the Lab Rats since the end of season 1. He reveals to the Rats that he is in fact their “father” a fact that Donald Davenport reluctantly admits to later in the episode.

However, Douglas Davenport merely claims that he ‘engineered” them, and thus that makes him their “father.” He never claims nor is the subject even remotely raised as to how they were “engineered’ or even if they have biological parents of either sex.

Donald claims his brother Doug engineered them to be weapons for the military and that he wanted them to be heroes in their own right, so he took them from his evil brother when they were small children and raised them himself rather than see them become pawns in his brother Doug’s evil scheme. A fact that they tell him later makes him their real father in their eyes.

However, the term “engineered’ is tossed around loosely throughout the entire episode. How exactly they were engineered is never made very clear nor how they came to be born period. Are we to believe that they were test tube babies of some sort? If so, who supplied the original biological material so to speak? And how was it originally obtained?

Again, none of this is made very clear.

In fact, the episode raised more questions than it actually answered. What exactly the writers mean by “engineered” is left up to the viewers’ imagination. Did he take babies that were already born and add bionic parts to them? Did he genetically engineer babies from the womb to be born with bionic parts somehow? Again, none of this is explained or even broached in this episode.

Perhaps this will be explained more in a future episode or perhaps this is as much an explanation as we’ll ever get.

We’ll just have to wait and see….

They're humans that have had their respective natural strengths enhanced by the bionic chips that can be inserted/removed via the back of the neck. There was an episode where Bree got tired of not being a normal girl and she destroyed her chip, rendering herself to the way she would have been had she had a chance at a normal human life. Donald has had them for years so that he could have the time to train their human bodies to learn how to handle the enhanced abilities. If they were not human, they would not have to train. The training they are required to do keeps their bodies in peak condition, because if they were to stop, they would no longer be physically able to keep up with their bionics. I'd like to know if they really are related to Donald, or if Donald's brother acquired them by some means, though. That's something I'm still not clear on myself.

I may not be able to prove that God is real, but you cannot prove that God is imaginary.