既是.又是.还是.的英文语法是什么?最好有例子

both...and...
not only...but also...
He is both a good brother and a good friend.
He is not only a good brother but also a good friend.恩不错，那么 既是他的责任，也是我的责任 怎么说？This is both his and my responsibility.This is not only his but also my responsibility.