参考：
How many are there in your family?
你们家几口人?
"How many are they?"
“他们有多少人?”
"How many are there of them?"
“他们多少人?” 谢谢。它们有多少？怎么翻译，问别人这个数量时，又是多个的How many are they? How many are these/those ~ ?