Crank arms are not parallel to each other. What could have caused this?
Like you said, they are cottered, what makes them aligned is that pin through a hole, which at the same time tightens the crank arm around the axle.

If you google "cottered crank", you can see the spindle, which has a slot in each side.

My hypothesis would be: or the cottering bold got deformed, or the spindle slot itself got deformed, or both.

A bolder hypothesis would be twisting of the spindle due to deformation or cracking, but most probably the bearings would not spin freely (how are the cranks spinning, by the way?)

The side which appears on your photo looks OK from outside, the other side we cannot tell.

But for sure this is a VERY irregular situation, which demand a full disassembly of the system, and absolutely no use before that.