Therefore, in addition to couples, it is also possible to have a legal cohabitation with a member of your family whom you could not marry (a parent or adult sibling, for example).
However, you cannot enter into a registered cohabitation if you are married or already in a registered cohabitation.
A list of documentation you will probably require is below.
The registrar will then issue an 'act of intent to marry' () literally a 'certificate of residence for marriage'.
The one critical exception is parental rights, which apply automatically to a birth-mother's spouse if he is male but not if she is female.