He had left home..he probably had this planned for days.
Given the lack of boarding card check before security, the "local" rule at MAN where the clearing security officer checks may have meant that a kind soul thinking he was helping a harrased family through by not checking each kid's paperwork rigorously.
I have never come across a kind soul at MAN or BLK for that matter,,But if this is right, this kid spotted a chink in security others, not just a little **** might have also.
EuroWings says kids are not always under their parents control, I have not seen that, but I don't doubt EuroWings for one minute.
On the back of that, it must be a rule that parents keep control of their children, or they go to the back of the queue, to be processed at the end..
The only real answer is a dedicated boarding pass checker, they cost money, but is there an alternative?.