Lecture 3 Speech event

For this lecture, I have a a bit confused but very interested example,

When I was in Taiwan, I was in the boy school, this Speech event happened after class in our wind band office.

Genre: conversation

Topic: no

Purpose or Function: moonshine

Setting: After class, practice time but no one practice.

Key: free

Participants: me, my friend

Message form: common spoken Chinese, laugh, gesture.

Act Squence: none

Rule for Interaction: not polite, relax talk, loud(because everyone loud there)

..........................................................................

Here comes my question, we have group A and group B chatting there(I was in group A), but after I heard one of the guy in group B is talking about one of the game I was played, I was just interrupt their talking. After that, because of me, group A and group B became one group and had a same topic.

Can we say there was just one group in begining? or are they still two groups in the end?