你可以用这个句型来表示在某人回来之后：
"After they come back"
这个句型的来源是英语中的一个时间状语从句，它的基本结构是：
时间状语 + 主句
例如：
After they come back, we can start the meeting. (他们回来之后，我们可以开始会议。)
After he finishes his homework, he can watch TV. (他完成作业之后，他可以看电视。)
注意，在这个句型中，时间状语从句通常用倒装句结构，即将助动词或系动词放在主语之前。例如：
After he finishes his homework, he can watch TV. (相当于 He can watch TV after he finishes his homework.)
After they come back, we can start the meeting. (相当于 We can start the meeting after they come back.)
"After they come back"
这个句型的来源是英语中的一个时间状语从句，它的基本结构是：
时间状语 + 主句
例如：
After they come back, we can start the meeting. (他们回来之后，我们可以开始会议。)
After he finishes his homework, he can watch TV. (他完成作业之后，他可以看电视。)
注意，在这个句型中，时间状语从句通常用倒装句结构，即将助动词或系动词放在主语之前。例如：
After he finishes his homework, he can watch TV. (相当于 He can watch TV after he finishes his homework.)
After they come back, we can start the meeting. (相当于 We can start the meeting after they come back.)