A group marriage may or may not involve bisexuality, and may be closed or open. Secondary relationships can grow into primary relationships, and they can also co-exist with a primary relationship, in the sense that the same relationship might be secondary for one partner, but primary for the other. An example of this co-existence might be a married person who is having a secondary relationship with someone who is not currently seeing anyone else, so therefore considers the relationship to be primary at the time. This person may meet someone later and develop a primary relationship with them, and may or may not move the pre-existing relationship to a lower level, depending on the choices of the partners involved. These are slightly less intense, but still practiced on a regular basis.
Secondary relationships are very common among married polyamorous couples.
They generally involve sex or some sexual activity which perhaps grows with the relationship. Secondary relationships are not much different from the conventional dating scene, where two people spend a good deal of time with each other enjoying similar interests and have a sexual attraction to one another. In a case where secondary and primary relationships co-exist as mentioned above, the person who considers the relationship primary has the benefit of maintaining a steady relationship, without feeling pressured to move the relationship up to marriage, or to spend more time than they are comfortable with in the relationship. These relationships can be very appealing to people who feel they do not have the time to currently involve themselves in a relationship that may lead to marriage, and may require more time than they can give. They are also appealing to people who want a steady comfortable relationship, but are not interested in marriage at all, and do not want to feel that their partner may want more from them than they are willing to give.