How should I ask these two questions in Japanese?
1. What's the closest thing you have ever done with your sister?

2.What do you like most about your sister?

Thanks!

Question

How should I ask these two questions in Japanese?
1. What's the closest thing you have ever done with your sister?

2.What do you like most about your sister?

Thanks!

Answer

2. 「お姉さんの一番好きなところは何ですか？」or「妹さんの一番好きなところは何ですか？」, depending on whether the sister is older or younger than the person you are talking to.

1. I guess「お姉さん（妹さん）との一番の仲良しエピソードは何ですか？」or something alike is what you are trying to say, but I'm not absolutely sure what you actually mean by the first English sentence.