This is coming for the mouth of a straight woman who has chosen to have many past lives a male, those of which I have been gay myself.
How gay couples, or twin flames, work is that spirits are genderless. We have preference to be in a female body or a male body; some are more certain about it and others are more flexible like myself (if you are certain female your twin flame will most likely be male, and vice versa however if you don't mind switching roles or having a gay incarnation this can be changed- you will also find transgender people to be the more "i'm a soandso gender soul, but i've agreed to take this gender even though I know I will be unhappy"). You will always be sexually attracted to the form that your twin flame/soul mates take, whether you choose to incarnate as separate sexes or the same because you intuitively know what form they will take.
People say it is impossible for gay couples to be twin flames and it makes me want to bang my head against a wall because they don't understand how it works.
The spiritual relationship is what matters, sure I was surprised to see myself doing the deed as a male with another male in a past life regression meditation but I knew it was true and from there my understanding of how sexuality works has improved tremendously.
(Btw, when I said I was straight I meant I was mostly straight cause I'm pretty sure my partner will be a boy however if he turns out to be a she I will understand.)
I know this is a short rant, but to sum it up; gay couples can be twin flames because it is not the physical body that matters (as this can be changed every lifetime) but the spirit.
Love and Guidance,