Mistaken Relations

Today, I have to blog about something both interesting and slightly disturbing that happened to my guy and I over my lunch break. We were paying a utility bill - scene: I was sitting in a chair across the desk from the teller with my guy standing behind me rubbing my neck. After the transaction was completed the teller acted like she wanted to say something but was having trouble finding the words.

Finally she pointed back and forth to both of us and asked "husband and wife?". As much as I would have like to have just said yes, I told the truth and shook my head no. She then proceeded to ask us if we were brother and sister then. OMG - NO!
That answer was nearly shouted by the both of us. We are still not sure why she would think that we were brother and sister after seeing him rub my neck the way he was doing. She told us that we resembled each other. We have been told that before even though neither of us see it. If it weren't for the fact that I don't want to post personal photos of anyone, including myself, on my blog, that would be the question I would have for you today.
The teller finally got the right combination of "boyfriend and girlfriend" right. But the baffled thoughts of our mistaken relationships had already done their damage for the day. Ten minutes later I had to force my beloved to "take the brother/sister thing and throw it out the window" since he wouldn't stop talking about how inappropriate the thought was, especially after the teller saw him rubbing my neck, and that even twenty generations ago our families were unlikely to be related, and so on and so forth.

Now that I have been mistaken both for my boyfriend's sister and years ago mistaken for my brother's wife (even more disturbing and grotesque), I ask you: have you ever been mistaken for a partner's sibling or a sibling's partner?