I don't know, do your thing! An actual monogamous relationship takes exclusivity a step further, when you can commit to a future with this person. Relationships have the future in mind.
You know each other's families. A relationship is an investment in the future and is not something that should be assumed. This is what it means to be in a relationship. So if you're wondering if you are exclusively dating or you're in a relationship with your partner, maybe refer to this article to find out.