This is one of two possible problems: shutter not functioning properly (with the curtains overlapping) or some object intruding into the light-path. I have had both problems occur in different cameras and both were fixable (by a competent repairman).
Is your shutter horizontal run or vertical run?
If vertical, it may be a shutter curtain problem, old lube and/or dirt (a CLA servicing the shutter curtains will fix it).
If your curtains run horizontally, it may be the some piece of material between the hinge of the mirror and the back of the camera body (opposite side to the lens mount) protruding into the light path. If this is the case, it should be easily visible if you remove the lens, set the shutter to "B" open the back of the camera and see if you can spot it intruding into the light path with the shutter open (at "B").
In either case, it is fixable.
Very interesing shots: you could claim they are genuine, on the actual day, ancestral candids?