Well, I saw that coming miles away. I wonder if it's true; it's almost too obvious. Who is this Source William and is his information reliable?
As to causing sibling rivalry, I doubt it; there is such a big age difference between the two. What's interesting, though, is that Grace would be Stefano's grandchild and EJ's niece. Stefano didn't even care to go the Grace's funeral, so I wonder how he will feel about that.