So... If I'm putting this together right, and I know my facts, Maddie's biological father artificially inseminated Patrick's mother, and thus Maddie was born to her parents... And she was adopted by Pete's parents... So, technically, she's only Patrick's half sister... But it's still a bit incest...
Author's response
Nope. Sorry to be blunt about it, but your completley wrong. It gets explained in the next chapter though, so don't worry