No, they do not. In fact, we have found that for most successful co-marketing partner relationships, its better to be in different, but-related industries.
A few examples help to illustrate this.
Two car dealerships probably do not want to be co-marketing partners because they are really competitors. But a car dealership and a mobile car detailer would make excellent partners since their businesses are related - but they do not actually compete with each other.
Two bakeries in the same area would probably not want to co-market together - but a wedding photographer and a baker would make a great pair. In this example - they are united by the common uses of their services (weddings, birthdays, etc) even if their actual industries have little relationship.
When matching parters, the BoostSuite algorithm uses dozens of factors to determine the best partnerships for your business- whether in the same industry or not. The most important factor is whether the audience of one business would be receptive to the products and services of the other.