My mom has perfect pitch; gets upset with early music ensembles tuned differently, goes mad when my brother and sister and I are all practicing at once in different parts of the house and she has to yell at all of us.
None of the three of us got whatever genetic component exists, although we've all had enough musical training to fill in the nurture part. sigh. I suppose it would be a hindrance in Sacred Harp, though, so it's a good thing I didn't end up with perfect pitch.

Chocolate Pi