A kind of relationship in which we can say anything to each other would be ideal.
"A kind of relationship"＝「ある関係の種類」
"in which we can say anything to each other"＝「お互いに何でも言えるような」
"would be ideal"＝「は利用的だね」
A sentence in context:
"It would be ideal, but also difficult, to have a parent-child relationship in which one can honestly say both negative and positive things to each other."
Having a relationship where you can be completely open and honest with each other, no matter what, is really the ideal.
こんにちは！
ご質問ありがとうございます。
ご質問について、いくつか言い方が考えられますが、例えば、
Having a relationship where you can be completely open and honest with each other, no matter what, is really the ideal.
とすると、「何があっても、お互いに完全に正直でいられる関係が、本当に[理想的](https://eikaiwa.dmm.com/uknow/questions/37178/)だと思います。」となります。
役に立ちそうな単語とフレーズ
be honest with each other お互いに正直でいる
open communication 開かれたコミュニケーション
no matter what 何があっても
parent-child relationship 親子関係
参考になれば幸いです。
アメリカ合衆国 
日本 
