Support-group and People record association information is stored on regular form "CTM:Support Group Association".
The below join forms can also be used to fetch Support-group and People data directly. These join forms has more fields that can be directly used in reports or to export information. Use the join form that best suits your requirement.
Let know if this helps or if you have further queries on this.
Thanks for your valuable reply, am able to export support group and its member data successfully with using above mentioned form.
Thanks for the update and closing the thread. Good to see the issue resolved.