Default Windows 2012 server allowed only one connection and if you want more RDP connections, then the option is to go with the RDS. But if you want to allow two Admin RDP sessions, Then you can follow the below mentioned steps to enable that.
Go into Group Policy Object Editor and then find,
Computer Configuration > Administrative Templates > Windows Components > Remote Desktop Services > Remote Desktop Session Host > Connections.
Then disable the Restrict Remote Desktop Services users to a single Remote Desktop Services session as shown below,
If you want to update immediately, Run GPupdate command.
I have used this in my Azure environment. If you are also going to use this cloud environment, then you have to check whether there is an endpoint created for that particular VM and that is allowed. (Because of the security reasons you will be changing the RDP- 3389 public port and the source port. Then you have to make sure the given ACL is allowed to connect from the outside.)