Last year I was on a flight where a single dad and his two kids were split up. All were in single seats, one aisle and two middles, several rows apart. None of their seatmates would move. The kids were around seven and three years old. FAs were no help. I finally got a young guy to swap his middle seat (very near the front of the plain). He resisted, until I pointed out rather forcefully that he would be doing childcare for a three-year-old if he insisted on keeping his assigned seat.

Not so surprisingly, no one else would swap an aisle or window to allow the three to sit together. End result was that the dad sat alone in a middle seat about half-way back, and the kids were on their own in the second row of E+. Surprisingly, the older child did a great job of caring for and entertaining her younger sister.