Any self-respecting parent wouldn't consider it an "impossible result" unless they'd done everything possible to keep drugs out of their kids' lives. These dumb motherfuckers brought it into their home, and not just that, used it there. There is no impossibility from that point onwards, just grades of intentional and unintentional exposure. Doesn't matter if Aaron was also there, or if they kept the drugs under lock and key, or if the cocaine fairy teleported in, one of the first things you learn as a parent is that you're a gatekeeper for what goes on in the home and who enters it. It's not just drugs, it's everything. Whether it's securing knives, protecting open powerpoints, or ensuring you buy age-appropriate toys, any failure is first and foremost your failure because you own the space they're in and kids are fucking stupid.