Charlie
First regarding Xi Wang: What's changed since she was born? Are there any environmental indicators? Have you gotten any results back from the blood tests.
Also, you should go visit her. It'll make you both feel better, I'm sure.
Now on to the messier part. You have every reason to feel angry. Hell, I feel angry and I don't even know Bill aside from the fact that he's your brother.
And you aren't the only one feeling behind. Trust me. This week I opened my eyes and realized somehow everyone I care about is moving on with their lives and I'm not. It wasn't a pretty realisation.