Please forgive me if I am posting this in the wrong place. I searched around, and I didn't find any other thread concerning this topic - but I may have overlooked it!

I was recently re-reading Harry Potter and the Philosopher's Stone, and a question struck me. On page thirteen, Dumbledore says to Professor McGonagall: "I've come to bring Harry to his aunt and uncle. They're the only family he has left now."

Here are my question(s):

1. How could Dumbledore know they were his only remaining family? Was he not aware that Sirius was Harry's Godfather?

2. If he knew about Sirius, why didn't he leave Harry in his care as James and Lily wanted? Sirius had not attacked Peter at that point, so that can't be the reason.