Okay bogan (or redneck if your a yank) discover's alien ship thingy on the shore and take the two infants home with them, naming them Troy and Annette. The kids turn out to have super strength, speed, damage resistance, senses, heat vision and x ray vision (it's sort of a deconstruction of Superman). Ways they could take advantage of their adoptive kid's?
Endless ways! Depending on the superpower, they can force the kids to help them with illegal activity or face severe punishment.
Also possible old fashioned sci fi explanation for why their alien nature gives the kid's superpowers?
They could use their kids for menial labour, like cutting wood or ploughing fields. They could put them on display like a freak show. They could go to an agent and try to make them into celebrities. If the parents aren't too smart, they might waste the kids' powers on trivial things. Or the parents might be tricked by a ruthless agent, con man or businessman.
they have to be smart at the first place to want to use their kids power to their advantage, no matter how trivial the ideas are.
Having the parents take advantage of them would only work if the parents had something to hang over their heads, otherwise the kids would quickly leave the situation. It would even work if what was being used to manipulate them was simply the old line, we've done so much for you but of course that would only work for so long. Yes, I think many things the parents did to extort the use of powers from their kids would indanger normal people, like if they wanted to rob a bank the guard could easily be hurt or killed. But I doubt the parents would be satisfied with robbing a bank for very long. Power tends to bred powerhunger people. What was once wonderful, soon becomes not enough.
Well lot's of kids don't realize their parents are being abusive. OH how about trying to show of their kids talents by making them play sports even though they could kill someone.
Not if it was all they'd ever known. In my impression the most common error that people make in writing abused children is underestimating how much they will buy into what their parents say. Especially if they have no other role models, and if the parents are sometimes nice as well as being mean. Sure, around adolescence/adulthood they may start questioning their parents' ideas, but they won't know what normal families are supposed to be like because they've never had one. There are some people who accept an abusive parents' words all their lives. Example: my father has two older siblings. His brother, the middle child, was a troublemaker and delinquent from a young age, and his sister was given the job of 'keeping him out of trouble' by covering for him, supervising him, bailing him out, whatever was necessary. Their mother kept insisting he wasn't a bad kid, the cops just had it in for him. My uncle once commented: "I could murder someone and my mother would say 'the poor boy was provoked'." When I was a baby, my father found out my uncle was sexually abusing his children, and turned him in to the cops. The rest of the family rallied around my uncle and basically disowned my father. Fast-forward 21 years, my grandfather is dead, my uncle is dead, my grandmother is so senile she doesn't know which son is which, and my aunt still spends all her time defending my uncle's memory. She's told cousins of theirs not to hang out with my father because he'll take their kids away (the cousins are a lot saner than her and haven't listened). She is in her 50s and still believes all the messed-up twisted stuff she learnt from her mother. So it's not surprising for an abused kid not to rebel for a long time. As long as you can write it convincingly, you could have them believe for awhile and then rebel, like my father, or you could have them believe for most of their life, like my aunt. Parents have a powerful effect on a child, and it's not easy to reject what they've told you. Even my father often slips into patterns he learnt at home, such as hiding his feelings and putting up with stuff that we'd gladly stop doing if we knew it bothered him.
If the parents want to keep exploiting the children, they'll have to keep their true nature a secret. Assuming these would be the first extraterrestrial beings anyone from earth had encountered, even being found in the arse-end of Australia wouldn't protect them from the prodders, the probers and the government agencies desperate to learn their secrets. Any acts the children undertake, criminal or otherwise, would have to be performed in secret - with minimal chance of being spotted, or even suspected. As for the abuse/loyalty issue, you mentioned that the children were found as infants. Presumably they'd have no memory of their previous lives as they grew up, so could easily be convinced that the exploiters are their real parents and so have that family bond keeping them there. As Ettina also perceptively said above, how would they know what they were doing was wrong if it was all they'd ever known? If the redneck lived miles from anywhere - say, at a remote sheep station - the children could be home-schooled in such a way that their sense of morality is deliberately warped, so they wouldn't see what they were doing as wrong. If that was the case, some sort of external influence or stimulus would be required for them to realise what they have been doing is wrong. That stimulus might be the arrival of a nosey/interfering outsider, or the childrens' discovery of something about the world outside their experience, but until that happens they'd just do as they were told.
Would it make sense for the super senses when they kick in to help them realize their parents are not right. Like hearing the woes of a man they use super speed to steal groceries from his shop, knowing that it's not victemless, and that other people are not "bitches and arseholes" like they were told. Oh and does this sound like a better story? An alien couple is preparing to send their twin offspring into space, away from their doomed world; lamenting that they are sending their children to such a primitive world, with massively physically inferior inhabitants... that planet being Earth... the London Countryside... in 1846. So the two kids are found and adopted by a poor father of four, and his wife is less than happy. In this the dad would be a decent guy.
If one of the parents is decent, then the kids would be more likely to stick around. As well as the idea that they have other siblings. Assuming you don't have an evil disposition, when you have superpowers, or are stronger than others, the tendency is to feel the need to protect those you love. Which in this case could be the exact reason why they would allow themselves to be used. Mom says we have to steal groceries because otherwise we won't have enough to eat and we can't let tiny Tim go hungry. Even though they know that mom spent the grocery money buying shoes. I love the idea that one of the motivating factors in developing a conscience is overhearing or seeing the negitive effects their action have caused on others. Even though I like the story line about the couple sending their twins off into space, I love the story behind the children being used for their gifts and having to decide what they are going to do about that as they develop a conscience. I'm a big fan of back story and using it to make your story more full, so I tend to write the back story. Except I write the backstory in shorter length, a chapter or two. And then try to write the story without using those chapters at the beginning but sliding in a paragraph here and there. That would be hard to do if the kids had no memory of their parents or the previous world but you could maybe have a book or journal that came with them, that they find.
