There is no reason why you cannot run two admin servers on the same physical box provided that
1) they are not in the same domain - 1 running admin server per domain
2) they don't have the same ip/port - so you'd need to be careful and specify listen addresses and ports to prevent conflicts.
3) they have different server/domain names - WLS uses the names to lookup some component and naming can cause issues. It's documented somewhere.
But under same domain, I think they still will use the same JVM, I want to use 2 different JVM in this case, Is it possible to run 2 different instance s of weblogic server on the same machine but having 2 different JVM's.
Each server ( whether it's a admin or managed server ) use it's own JVM. If you want to use two Admin server ( which mean you should have to create two domain since each domain should have only one admin server ) then you can create and start, each will run on it's own jvm.