King Family in Accident After Speech Commemoration

Fifty years since "I have a dream..."

Martin Luther King Jr.'s family just got into an auto accident while leaving the rally to commemorate the 50th anniversary of his "I have a dream" speech … TMZ has learned.

According to sources on the scene … several of MLK Jr.'s siblings and grandchildren were on a charter bus leaving the rally when a van ran a red light … forcing the bus driver to slam on the brakes to dodge the vehicle.

MLK's sister -- Christine King Farris -- was on the bus at the time of the accident. Earlier in the day, the 85-year-old placed a wreath on the MLK Jr. Memorial.