I also hate when people line up to board early with kids as old as 12 years old. If they need more time to board, they should also remain seated at the end of the flight because they need more time to exit.
I personally don't blame families for giving it a shot.
The gate attendants are the ones at fault -- they need to tell the scammer family to get back on line.
I recently saw gate agents actually turn back folks trying to board when it was not their group. Was shocked as they rarely want to get into any form of conflict, especially in light of recent events. I'm at the end of priority boarding all the time so the overhead issue rarely affects me but I look at what some folks try and get into the overhead and I just laugh. Of course I also don't pay for my checked bag. So the thing that annoys me most is definitely the dogs, bagged or leashed, especially the BS emotional service dogs for idiot 20 somethings. Anyone travel with dogs? How much do they charge for that?