The rumored “gay gene” is known as Xq28. Xq28 is found on an X chromosome given by the mother’s gene. It’s believed to be what affects a male’s overall sexuality.
Because it comes from the mother, the gene does not rely on the homosexual sons. This breakthrough caused scientists to examine biological characteristics of the mothers.
In Italy, a test that revealed that female relatives of homosexuals have 1.3 times more children than the average female.
This would explain why the number of gay people is not decreasing despite same-sex couples not having children. A test is yet to be conducted on fathers. But it could be inferred that lesbians gain the same or similar gene from their fathers.
Another thing must be kept in mind. Humans carry the potential of having mutations every time a child is born. Genes have random sequences that serve no purpose in the body. Because of these extra random gene sequences, random mixtures can be made when having children. But these random mutations aren’t always activated.
Not everyone that carries the Xq28 gene becomes gay. People have genes that aren’t activated all the time. That means that while gay couples can’t produce children on their own, the gene can still carry on through their siblings. If the mother of the gay individual carried the gene along with the father, their genes would spread to all their children. Even if only one of them becomes gay, the genes could be activated in their sibling’s children.