Oh, love this! It’s so realistic, even if it is set in sci-fi. You’ve captured the sibling relationship perfectly and I really enjoyed it. Now I want to know if they’re going to get caught and/or what happens next. Well done!
I like the idea and the characters seem interesting. I’d be glad to see where this goes. Sadly, the nerd in me has complaints (GPS stands for Global Positioning System, it works on a planet surrounded by satelites, not in space. And stopping a ship in space might not be easy.. Sorry for being nitpicky.)
shadowlight 
nuclearsubmarine