Sorry to hear about your difficulties, However you are looking at a very close family group.
In the general mix of population the recombination factor could be about 10 to the power 8 per generation. It does predominate on the male side bceause of the Y chromosome ! I studied this at UNI and it was hard work then, but when you advance this theory into genealogy it gets a bit loose !
What this means is that,with the advancce of genetics,environmental causes,are now most likely to appear in families.