This is how I see marriage

humans
- id
- forename
- surname
- birthdate

binary_marriages
- id
- partner_1_id (foreign key references column humans.id)
- partner_2_id (foreign key references column humans.id)
- marriage_date
- divorce_date (NULL if still married)

"Honey, will you add a record to the binary_marriages table with my id as partner_1_id and your id as partner_2_id?"