Yeah, my Dad and I went on a trip to LA together recently and went to a fancy restaurant to celebrate our last night in town. We had to correct the waiter several times about what Dad's "lovely wife" would like. I ended up so creeped out, I didn't really enjoy the meal.
ETA: HA! DH just reminded me of when he, my mom, my sister, my brother, and I went on a retreat with an organization we were all involved in when DH and I were in our late teens. DH strongly resembles my sister, believe it or not. Both have intensely dark hair and eyes, tan easily and have very straight, pert noses. My brother and I resemble each other, and look a lot like my mom.
However, by the end of the week, other people at the retreat were completely confused about our relationships. (We didn't use last names often. Name tags were first name only.) The most common theory was that Sister and DH were my mom's kids- I was dating DH, and that my brother (then age 9) was our son. At that point, it was just funny to hear the different configurations. We didn't get offended.