I hate admitting that I know this...
Ephebophil used to be a member of another forum of which I was also a member. He posted a few videos like this. I have no way of knowing if they are a real brother sister couple or not, but I believe it's a very real possibility.
Personally, I thought the guy was a sexist jerk. He was very into dominating his "sister" and liked porn which featured women being humiliated (e.g., urinated on, spit on, etc.). In one of his videos he has his sister eat his ass. Someone replied that they weren't really interested in seeing his ass, they wanted to see her ass, so why didn't he make a video of himself eating her ass. I can't remember his exact reply (this was years ago) but basically he said that it was her job to service and pleasure him, not the other way around.
I really hope she smartens up someday and royally kicks his ass. Now that I'd like to see.