I don’t remember anything about the sister, but IIRC, the grandmother suddenly became ill when the campaign and questions about his birth were heating up. He went to see her in Hawaii and she died while he was there or right after he left. Just a few days before the election.
The whole thing was creepy/suspicious.
Yes. Clearly for some reason, Typical White Granny had to go. Maybe she was still quite with it and would have spouted off that he wasn’t born here.