The sibling relationship in this story was very realistic, I thought.
I also was impressed about the use of all 3 dimensions in zero G. Which is why I was particularly disappointed about the cavalier approach to vacuum in the story. Vacuum is very different from no air. Yes, there is a lack of oxygen, but there is also extreme low pressure, which wreaks havoc on the body. You can't just strap an unsuited body to your back and hope they last until you can get them to oxygen. You literally have only seconds before irreversible damage happens, when the fluids in your body start boiling and breaking cell walls.....