Currently, there is no one known gene that causes all, or even most of, Tourette's. Sorry, but if you don't know your family history, then it's not as if anyone, even the most specialized doctor or geneticist, could predict the likelihood of your child having TS. the data that exists right now isnt' even ready to test for the genes to predict TS in anyone--at all. If you're still worried, I guess you could talk to your doctor or your brother's doctor, but in terms of predicting if you carry the gene-there is simply not the knowledge or the technology to test that. Even if you did, it's not as if your child would end up with a life-ending, or even a very severe (TS is usually fairly mild, although severe cases can occur) disorder.