Are you related to the Blahs?

My name is David Blah.
-- "Are you related to the Blahs?"
No.

I know all of the members of my branch of the family. I could draw the tree from my great great grandfather. However, I firmly understand and accept evolution and clearly am related to the the Blahs. But, not in the fashion they want to know about. -- Every time I say "no" to that question, I feel a little tinge like I should have a witty reply ready that doesn't violate common ancestry.

Any suggestions?

I am more related to them than to bananas, but my surname does not reflect a particularly close or known relationship.