According to my personal experience makes writing a research paper look easy, It is completely understandable that you may not be able to think for yourself and come out with a topic your paper can score well on. First you write all thing that you have in your own mind with imagination after that you have better option to choose proper word according to your topic.
Best of luck.
Well, your thesis is going to depend on your introduction; it should flow from it. But assuming you can handle that transition, and you're going to address the key points you put below, I think this might work as a thesis (provided that in the prior sentences, you address the ideas of gay parents affecting their children):
But in light of the fact that parental sexual orientation doesn't affect children's mental development, allowing so many children to wait to be adopted or go to foster care is not only irresponsible, but even harmful.
You then go on to prove or provide evidence for why gay parenting won't affect children, a paragraph on the need of children (with some statistics on why foster care is so apparently unhealthy), and finally your conclusion that because it's not bad, and so many kids need adoption, we ought be pro-gay adoption.
Hope that helps!