You have several options:
1) use 2 last name fields and two first name fields in your record (simple but messy).
2) Make your table structure more sophisticated.
You could make a "people" table with the following fields:
Make your other table a "contact info" or "Couples Info" table give it whatever fields you now have for recording data on your couple, addresses, phone number, etc. but add one more field: CoupleID and make it an auto-entered serial number.
Create a relationship: People::CoupleID--=--ContactInfo::CoupleID and enable the creation of related records in the People table.
Now put a portal on your contact info table to display related People records.