Riku doesnt have a nobody because he chose the dark side. He also never turned into a heartless like Sora. And then he got stuck in Ansem's body. As for Sora's parents, they are on destiny island. I wonder though did they ground sora when he got home XD
Sora: But dad I was on a gummy ship traveling worlds and defeating heartless.
Dad: Enough with the lies go up stairs you are grounded
Mom: i was so worried I thought you were dead.