On Ryanair, the only way to guarantee that your party sits together is to purchase reserved seats during the booking process or via the "Manage My Booking" section before check-in. If you choose the "Random Seat Allocation" (the free option), Ryanair’s algorithm will frequently separate passengers on the same booking, even if there are adjacent seats available. This is a core part of their low-cost business model. For families traveling with children under the age of 12, Ryanair has a "Family Seating" policy: one adult in the group must purchase a reserved seat (usually for a discounted fee), and in return, the children in the same booking receive their seat assignments for free next to that adult. If you do not pay for seats and find your group separated, the cabin crew is generally not required to move other passengers to accommodate you, so pre-purchasing is the only reliable way to ensure a shared flight experience.