If your seats are not together at all, you will want to create separate listings as we guarantee seats will be together if 2 or more are bought on the same order.
But, there is a chance they are still together.
If the tickets are for an event at a theater, the seats may be next to each other, even though the numbers are not. It is common for theaters to have odd and even seating depending on the side of the stage you are sitting in. For example, 13,15 are together on stage left and 4,6 are together on stage right.
If the event is a general admission event (no seating), then the numbers on your tickets are used for tracking purposes of how many tickets were issued out in that batch. It's okay to list them together as there is no seating.