Per the 5 CFR 890.302 an exception can be made for an FSO and their spouse to have FEHB.
§890.302 Coverage of family members
(a)(1) An enrollment for self and family includes all family members who are eligible to be covered by the enrollment. Except as provided in paragraph (a)(2) of this section, no employee, former employee, annuitant, child, or former spouse may enroll or be covered as a family member if he or she is already covered under another person's self and family enrollment in the FEHB Program.
(2) Dual enrollment. (i) A dual enrollment exists when an individual is covered under more than one FEHB Program enrollment. Dual enrollments are prohibited except when an eligible individual would otherwise not have access to coverage and the dual enrollment has been authorized by the employing office.
(ii) Exception. An individual described in paragraph (a)(2)(i) of this section may enroll if he or she or his or her eligible family members would otherwise not have access to coverage, in which case the individual may enroll in his or her own right for self only or self and family coverage, as appropriate. However, an eligible individual is entitled to receive benefits under only one enrollment regardless of whether he or she qualifies as a family member under a spouse's or parent's enrollment. To ensure that no person receives benefits under more than one enrollment, each enrollee must promptly notify the insurance carrier as to which persons will be covered under his or her enrollment. These individuals are not covered under the other enrollment. Examples include but are not limited to:
(A) To protect the interests of married or legally separated Federal employees, annuitants and their children, an employee or annuitant may enroll in his or her own right in a self only or self and family enrollment, as appropriate, even though his or her spouse also has a self and family enrollment if the employee, annuitant or his or her children live apart from the spouse and would otherwise not have access to coverage due to a service area restriction and the spouse refuses to change health plans.