Not AF but ST nonetheless - I flew frequently DXB-JED/RUH and in transit to CDG. I would say that SV must have at least 3 to 4 fraudulent passengers in J, every single time, usually local teenagers. The argument being used here is: I usually fly J but the tickets were oversold. Witnessed it at least a dozen time. Most of the time, sent to the back, but noticed some FA not arguing (most of the girls FA[hum..the ones actually working...hum] don’t speak Arabic, and pax would (pretend to?) not speak English). And they wouldn’t receive any support from their male counterpart. Side note, a flight on SV is an adventure of itself

Not sure this is fraudulent, or just the usual "f*ck paying customers, spoils go to friends and family first":

My son flew as a UM on a long haul flight. Seat next to him taken by another kid, who after take-off was moved to Premium Eco by his mother, whose mother was an FA (bot not on this flight). Not supposition, but words of the kid himself who probably wasn't aware of the sensitivity of this topic and with infantile naïveté told the story to his seat neighbour (=my son).

Seriously, couldn't they have found one passenger in Eco that has status or some other characteristic that would have made him a better candidate for an op-up than the 12 year old offspring of a flight attendant?

has KLM already contacted you for donating all your KLM memorablia for a museum.

I have seen a lot of split of family Y/J or J/F
almost each time it’s a mess and disturbing other PAX.
so sorry to appear to be rude, but I consider that everyone should select the same cabin . It would shut down these kind a painfull situations for familles and other PAX

I don't disagree with your principle, but I disagree with your reaction to this specific anecdote shared by pjhartog.

It seems absurd having to pay UM fees despite parents travelling on the same flight (I am saying "it seems", because I actually happen to understand the AF logic: it's for safety/evacuation. UMs are all in a designated part of the cabin with FAs close by, and there is a protocol in place how the FAs take care of the UMs in case of an emergency. That actually does make sense. Taking it to the extreme and demanding that kids go through the separate UM check in and boarding process at the airport is ridiculous).

Second, I don't have an issue with a case described by pjhartog: kids joining the parents for the final 20 Minutes of the flight, when all the service is done and the cabin is prepared for arrival. They do not get a more comfortable seat for their trip, don't get the service and catering of the higher cabin, etc. They are just closer together for disembarkation. Could they have waited for each other after disembarkation? Sure. But if they choose not to and the cabin crew lets them, it wouldn't bother me a bit.

Other than that I agree with you: people who think they can basically spend their flight in the higher cabin only because there is another family member there, contant back and forth, etc. Very annoying for others. And if you go upthread where I describe the case of how a family of four with three seats in P basically got their second kid into the P cabin from somewhere behind/upstairs for most of the flight including the full sleeper and breakfast service, then you have proof how much I agree with you that this family reunion during the flight is annoying.

And since we are discussing people in the wrong cabin: I get very annoyed when boarding the Business cabin on a Euro flight, with only one other passenger in the four rows of J class, but all overhead bins packed with stuff from people who just left their luggage/shopping bags/back packs/tajines/paintings in row 2 on their way to row 29. And I also get annoyed when queues of Y travelers form in the J cabin waiting for the restroom. I get it, it's less comfortable to walk from the front of the Y cabin all the way to the back and having to wait there and to be blocked by the drinks cart - but if you don't want that, pay up.