Applicants wishing to enlist in the US Military, and are married to a military member can generally enlist without a waiver, as long as there are no children in the household. However, applicants should understand that there is no guarantee that they will be stationed at the same base as their spouse. For details, see my article about military couples.
If there are children in the household, the applicant is disqualified for enlistment. The active duty services rarely waive this, while the reserve forces (Reserves and National Guard), often approve waivers, as long as the applicant can show a workable family care plan.