There appears to be a link to how a woman's X-chromosomes are inactivated and to her propensity to have multiple gay sons.
However, it appears that this does not occur in the majority of mothers who have multiple gay sons but only in about 25% of them (as opposed to 13% with one gay son and 4% with no gay sons).
How this affects the "germ theory" of Greg Cochran, I am not certain. But it hardly refutes it, as it occurs in a relatively small number of mothers whose sons are gay.
That is all.