Coincidence?

I have just been told by Callum, my x husband, that his best friend and co worker's son has been diagnosed with leukemia also. Very early days and not clear on the exact type yet.
The two of them worked together for about 10 to 12 years, they were lumberjacks and exposed to constant exhaust fumes (benzene!), both Scott and the other child were concieved during this time. The only other man they worked with died of lung cancer.
I had read before about pre-natal paternal transmission and thought this could be the cause of Scotts leukemia. I never really dwelled on the cause too much, it didnt matter, only cure mattered, and still does.
This news is very sad but also very eerie too.