How to Request a Relationship With Someone on Facebook
If you have been dating the same person for a while or have recently been married, you and the other person may want to set your Facebook relationship statuses to represent your involvement. You can set your relationship status and choose a person from your list of friends, but the other person must confirm the status before it will be displayed on your profile. Relationship status changes are available right from your Timeline.
Click “Update Info” from your Timeline.
Click “Edit” in the Relationship box.
Choose the relationship status that best applies from the drop-down. Type the name of the person you're in a relationship with to add him to the status.
Select an anniversary date, if desired. Additionally, choose people to share the update with via the audience selector.
Click “Save.” The other person will receive notification of the status and will have the option to confirm.