Romney admitted he lied about his father doing so:
http://www.timesonline.co.uk/tol/news/world/us_and_americas/article3082350.ece
Mitt Romney forced to backpedal over Martin Luther King claim
Romney had to admit he didn’t actually see it. But other witness claim they did see the two in the same march.
For me, no big deal. The point was that George Romney was a champion of civil rights. Good for him!