Did you purchase the tickets in one single order? Then chances are you will be seated right next to each other. The ticketing system clearly indicates during the reservation process if your tickets would not be located next to each other.
There are 3 venues (Sportpaleis, Lotto Arena and Vorst Nationaal) where one physical block has 2 numerical blocks, e.g. block 118/119. The numbering of the seats runs from seat 1 to 8 in block 118, and then from 8 to 1 in block 119.
Therefore, in the middle you will find two chairs with the same (chair) number, but in a different block. However, not all blocks contain the same number of seats, so other combinations than 8-8 are also possible.