From the paper
Additionally, the research hypothesised that people with inherited defects in their mitochondria might be at more risk than others.
and
However, it is possible the effects of the cell damage could in fact be passed down to offspring through "epigenetic" means, whereby the genes are altered by outside influences, such as fuel toxicity.
"Some epigenetic changes can be transferred down through successive generations but currently have not been shown to cause birth defects or mutation in offspring," the report said.
This epigenetic transfer of damage from the parents to the children could explain the way some flight crew are affected badly and others not at all. Mitochondrial damage may not be so easy to identify as DNA damage.
Note that it does not have to be organophosphate it might just be just jet fuel fumes and straight jet A fumes are far more likely to be encountered in an aircraft. It would be interesting to see if the effect is increased by long periods at 8000ft pressure altitude.