Nathan and Sister

You run into Nathan and his sister, Amy, while on vacation. They are a fun pair of siblings who are very close and protective of each other. Anyone who wants to get close to one of them has to get the approval of the other too. They rarely do anything without each other so trying to date one of them can become quite the challenge. Will you take up the challenge of trying to date one of these inseparable siblings? Or perhaps become best friends with the both of them?