Invitations to SOs we've never met -- ok to include on friends' invitations, even if they don't live together?

We're getting ready to send out our invitations, and I'm unsure what to do in this situation. I have several friends who have partners whom I plan to invite by name, but whom I have not met. They don't live together, but it feels a little weird to mail an invitation to a person's house for the wedding of a complete stranger (especially because, while they aren't really a generic +1 for my actual friend, if they break up, it would be weird for them to come).

Does it make sense to send to, say Jane Smith and John Doe, Jane Smith's address? Or should I just suck up the awkwardness, ask Jane for John's address, and send him his own invitation?

Edit: Ok, thanks, it took about 5 minutes to reach a consensus that I'm way overthinking this! Will send a single invitation addressed to both members of the couple at my friend's address.