A spouse in L-2 status is employment-authorized incident to that status. The family relationship has to be a legal marriage recognized for immigration purposes; a common-law partner is treated differently.
Marriage, not cohabitation, determines L-2
Hypothetical example: a Quispamsis delivery director has lived with her partner for nine years but they have never married. L-2 status is available to a spouse and to unmarried children under 21. A common-law relationship, even one recognized in New Brunswick, is generally not treated as a marriage for U.S.
immigration purposes, so the partner would not qualify for L-2 status and would need his own basis for entry and work. If the couple marries before the petition, the spouse can seek L-2 status and would be employment-authorized incident to that status once admitted. This is a fact that has to be decided by the couple, not a paperwork issue, and the reviewer should be told the actual relationship rather than an assumed one.
Children under 21 of either parent may qualify separately depending on the parental relationship.