Passengers with pre-selected seats are guaranteed the same seats they have pre-booked online unless if the flight safety measures require otherwise.
Passengers are seated on first come first serve basis. Families are considered in assigning them with seats next to each other whenever possible and subject to seat availability.
However, to ensure proper seating for families it is always advised to pre-book seats at the time of booking. Children below 15 and passengers with a special need are not allowed to obtain seats on emergency exits.