That's what Mitt claimed in a 1978 interview with the Boston Herald.  That is, that he and his father, George Romney, joined in marching with Dr. King.  "My father and I marched with Martin Luther King, Jr. through the streets of Detroit."  An article by Michael Levenson in the December 21 issue of the Boston Globe refutes this claim, too.   I missed it in the Globe.  But a friend called to my attention Andrew Sullivan's posting the same day about this false claim.  This "marching" is not just a metaphor.  It is an out-and-out lie, and apparently a habitual one.  That makes good old Mitt a pathological liar.  And, of course, given our last two presidents congenital aversion to the truth, this is also a qualification for the office.

Apparently, there are cognate claims all over the web.  Here are two:

Joshua Marshall: "My dad sailed with Columbus."

Another: "My mom dated Jesus."

You are welcome to make up others and post them here.