Kalyana,
Are you saying that your parallel DEV systems both have the same SID? When I've done this in the past, the parallel system had its own unique SID, and so this would not be a problem. You can definitely have multiple entries in the services file that share the same port, as long as the SIDs are different, i.e.:
sapmsDEV 3600/tcp
sapmsDV2 3600/tcp
sapmsQAS 3600/tcp
etc.
--Matt