The coppers you spoke to in passing were probably general duties uniform ones who probably don't give a damn about traffic stuff. Us traffic fanatics are rather hard to come by sometimes as the general belief is that traffic offenders aren't "real crooks". So really they wouldn't know what they're talking about anyway.
The information so far is correct that you are allowed one passenger between 16 and 21 (inclusive). Any passenger between those ages doesn't count if they're a family members. The excuse of, "Um, ohhh, yeah he's my cousin" doesn't cut it, nor does he's my brothers, mates, dad's girlfriend. In other words you're allowed to drive younger brothers and/or sisters to school or footy etc.
However.... if there's a fully licensed driver seated in the front next to you, then all bets are off and you can load the car up with as many passengers between the restricted ages as you like. Therefore if you can get someone with a full licence in the car, get them in the front and you can take everyone.
