"That person is neither gay nor straight."
Translation:Die persoon is noch homo, noch hetero.
Not everyone chooses to have kids. Currently, the only way to have a kid is with an ovum and a sperm, or cloning (which has serious health implications for the child, so is unethical). One day science will probably find other ways to have children, but for the moment it takes a man and a woman to make a child, even if it's conceived in a test-tube. Two lesbians can't have a child without involving a man and two gay men can't have a child without involving a women.
It's simply a matter of what's physically possible. Human physiology dictates that we can only naturally reproduce sexually, i.e. one male, one female. Science may eventually make it possible for us to reproduce unnaturally, i.e. outside nature. If/when this happens, it is up to each society to judge whether this is a good or a bad thing, and whether they find it acceptable or not.