Not strictly genetic, certainly, but in at least one configuration there is a clear effect that is perhaps genetic in the mother:

> Biochemical evidence for this hypothesis was identified in 2017, finding mothers with a gay son, particularly those with older brothers, had heightened levels of antibodies to the NLGN4Y Y-protein than mothers with heterosexual sons.[1][2]

https://en.m.wikipedia.org/wiki/Fraternal_birth_order_and_ma...