How did the flight attendants let them get away with stealing seats and occupying more seats than they had paid for? It must not have been a full flight if they used 3 seats when they'd only paid for two. And I would think safety regulations would prohibit a child too large for lap baby status from sitting on someone's lap.
Gate agents are responsible for getting the flights out on time, and it's often interesting to watch the interplay between the gate agents and the flight attendants on matters like this. The flight was plenty full; what this family did was essentially demand that others move around to accommodate them and by the time someone said they wouldn't move (triggering the challenge by the FAs for boarding slips), the gate agents were in the "hurry up, we gotta close the door and shove back from the gate" mode. The mommy was traveling with her own dad and mom, and the father had taken the aisle seat and "shamed" anyone wanting their own assigned seat by saying "you don't want to sit next to two kids, so go to another row."
The mommy compounded the fun during the flight by repeatedly trying to slam her seat back (she was right in front of me) and could not, so she'd glare at me as though I were denying her the sprawl. Hey, I was in an exit row, which mean that her seat wouldn't
recline - by law. The passenger next to me told me that the family originally tried to occupy our exit row, but the flight attendants had them move - since you can't have children in an exit row, especially not lap "babies." According to my seatmate, mommy was crabby about that because she wanted one or more of her babies to be able to lay down in the additional legroom area that exit rows feature.
Oh, they were special to the max.
They had gotten on our flight early (and staked out their special seats) because "gramma" needed a wheelchair for boarding. Well, as often happens on flights to vacation destinations, mine was a "Miracle Flight." Miraculous, because the very same people who have to be carted on board via wheelchair and thusly gain early boarding (along with their entourage,) miraculously become spry and agile upon landing - as was the case with gramma, who charged out of her seat two rows behind me right before the seat belt sign went off at the gate after landing, to start flipping up the four different overhead bins where their stuff was stashed.