Finding Groupid from userId and finding users under group

Hi all,

In SAP EP, 5 users are created (IN_COM_APP1,IN_COM_APP2,IN_COM_APP3) and client has not given group id which is assinged to those id, So can anybody tell how to find Group id from gives user id, and once if i found groupid, how to find users under that group.

Thanks,

Satish