invite address question

ok i have a dumb question...

if the guest i am inviting is the female...do i address it to the male still?
example i work with Jane...so on the invite do i address it to Mr. & Mrs. John Doe?

also if its 2 people who are dating do you put both their first and last names on seperate lines?

'Proper etiquette' calls for married couples to be addressed as Mr. and Mrs. John Smith, even if you know the woman better. I didn't follow this rule for all people. For example, I've been friends with this woman for years and she recently got married. I addressed the invitation as John and Jane Smith. I didn't feel the need to be super formal with her and I really wanted her name on the invitation. For elderly couples or people who are more traditional, I did Mr. and Mrs. John Smith.

For couples living together or getting one invitation, I put both first and last names of each person on seperate lines. For example:
Mr. John Smith
Ms. Jane Doe
123 Main Street
Anytown, State Zip