[juanfzapata]

If I belong to a group, and I am chatting with one of the members, can the other members read the conversation we are having?

[Michelle Haag]

If you have added that person to your BBM list, and the conversation is in regular BBM outside of the group, then no they can't read it.
If you just started a new chat within the group, and you and the other person are the only two talking, then yes the others can still read it.

[andyahs]

If I belong to a group, and I am chatting with one of the members, can the other members read the conversation we are having?

Only if the chat is within the group.