Paternity test?

Hi, I have a question about paternity tests and I'm not sure where to go to find answers. Google doesn't even seem to help. I'm pregnant, and there are two possible fathers. They are half-brothers. I know brothers share the same genes, etc. but I'm wondering if the test will show the definite father or what the chances are of an incorrect result? It's very important that I find this out as I love one of them and know he would be a great dad. On the other hand, the other guy is a jerk who ended up raping me because I turned him down. I need answers and don't know where else to go.