あなた達は一緒ですか？って英語でなんて言うの？

"You" can refer to either one person or more.

The first two sentences can be used if you just want to know if they came to the location together. Perhaps they would like to sit together or be near each other depending on the circumstance. The third sentence can be used if you need to collect a fee for something and want to know if they should be charged as a group or individually.

These phrases help to understand the composition of one groups of people

You can simply ask "Are you two together?" "excuse me" will get their attention and the "are you together" asks your question.

When people are cuing up it is difficult to gauge if they are alone or part of a group. Best is to inquire if its a single individual or a group of people.

1. Are you guys together? By asking this question, you are asking if the people are in one group. The expression "you guys" refers to all the people in the group.

To ask customers if they are in a group or not, you can say: "Are you guys together?" "Are you in a group?"