But according to a topic made not so long ago the homosexual person is born with a different "brain" than the heterosexual.
No, it was found out that homosexuals
have different brains than heterosexuals. It did not prove that they were
born with different brains.
What if the person is heterosexual and is given to a homosexual couple? Isn't that a bad environment to be brought up in?
There is no correlation whatsoever. Children that are raised by a homosexual couple don't have a higher chance of turning out homosexual themselves. This is a myth propagated by those against homosexual marriage, and it's long been dispelled by real-world experience from countries that have legalized adoption by homosexual partners.