In all the episodes I've seen they call him Davenport, but they refer to him as his dad. I've always been very confused to as is he their biological father or adopted? I assume adopted because if biological, what happened to their mother. If they are adopted I'm curious as to weather all three I them were adopted seperetly or are Adam, Bree and Chase are biological siblings? Just very curious.
Adopted. It turns out they don't have biological parents, not exactly. Donald's mad (and I mean genuinely mad as in sociopathic) scientist brother grew them in a lab (as such all three are biologically siblings, its unclear where Douglas got the genetic material from, though its implied he used his own DNA) to use as test subjects for the bionic technology, once he discovered robots burned up after a few years.
Discovering this Donald took them away from his evil brother, Douglas faked his death to escape the authorities. Donald couldn't undo the process, but took them in and raised them, its implied he honestly never felt like he was truly there father until they told him he was.
Not exactly, depending on the rules, its possible he could have grown them by manipulating his own DNA. If they do have a mother, it could be any woman who he took a DNA sample from.