German phrase
Kennen Sie sich?
Meaning
Do the two of you know each other?
When to use it
Asks if they are acquainted. It politely addresses two people.
Example dialogue
Entschuldigen Sie. Kennen Sie sich?
Excuse me. Do the two of you know each other?
Ja, wir kennen uns von der Arbeit.
Yes, we know each other from work.