Just an FYI, I've never read the books, but I'm going to invest my time in the series. For those that are trying to figure out who is who and the relation of each of them to each other, HBO has done a nice job with the Viewers Guide.
HBO: Game of Thrones: Viewer's Guide
I was confused at the end because I thought the Queen was having sex with a guy I thought was her brother and now after going through the guide I was assured that my initial understanding was correct.