Sam's family or pack told Max's parents beforehand about their kid's (and probably to an extent their own) lycanthropy
This could be why Max's father doesn't seem to question if raw beef is good for Sam's health when the kid tells him how he prefers his burgers. Also, if Max's parents were around to see Sam's transformation, they didn't seem to be as shocked as the kids were, Max's mom only saying the next morning that Sam is an 'unusual boy' as she smiles. Sam's family could be...
- A pack of werewolves.
- to an extent, he could have Massive Numbered Siblings similar to the pups from Hotel Transylvania.
- A family of different creatures a la The Munsters, bonus points if he also has a vampire mom and a Frankenstein's Monster dad.
- Humans, with the possibilities of him being either adopted or cursed.
- A human mom and non-human dad or vice versa.
