It is possible. quite possible to. Done it myself before a few times
Step one: you will need to open your Database program you use to look/edit your database like navicat or heidiSQl or what ever and run a back up of your World database + char database and after the back up's are done on both database's or if you got world database already like you want to use 2 dif one's you already got
then just make a new database name it World2 and make one more and name it char2 or what ever for the char database and inport the world database in the world database you just made and inport the char database into the char database you just made and then go to your world config file (Note this is if you using trinity) and open the world server config and go down to the Database config and change the configs so it will conect to your 2ed database you just made the 2ed core you using so it be like main realm config =
Auth server username,password,Auth
World server - username,password,world
char - username,password,char
and the 2ed config file for your 2ed core should look like this
Auth server username,password,Auth
World server - username,password,world2
char - username,password,char2
so it will load your 2ed world for your server core/realm and change the ports such as world server port to something else then what it is
then last change the realmid and add the realm in the database under Auth > realmlist and add it there and load the 2ed world and that how you make 2 realm
Credits
Tutorial from Ghostcrawler336