2008 R2 RDP Users added to Remote Desktop Users group and local admin group

We have setup a new 2008 R2 domain with a separate DC and TS server. I have verified countless times all permissions, local security settings and RDP configuration. I have an issue where a user who is a part of the local RDP group logs in just fine but after logging in they are added to the local Administrators Group. Can anyone tell my why this might be occurring? I am pulling my hair out trying to figure out whats up.