Two people can live together and found a family without marrying or forming a civil union. They are considered to be in a de facto union, and each is the de facto spouse of the other.
If you are in a de facto union, the couple you form with your spouse may, or may not, be recognized under certain laws, depending on how they define a de facto spouse. Under the Civil Code, de facto spouses do not have the same rights and responsibilities as spouses in a marriage or civil union, however long they have been together. For example, if your de facto spouse dies, you will not automatically inherit, unless you are named in the will.
However, your children's rights are not affected. All children have the same rights, whether or not their parents are married.
You and your de facto spouse can, if you wish, define the rights and obligations you wish to recognize, for example by making and signing a cohabitation agreement.