yum:How can I instruct yum to install a specific version for X

I have to implement two yum repos, **x** and **y** which contains same packages with different versions. If a user do: 1. yum install x - should install the latest packages of one branch 2. yum install y - should install the stable version from different branch When I execute yum install x, installs the latest version package from **x** repository, but when I execute, yum install y, doesn't work as expected though I have created meta packages. I have experimented with yum plugins protect, priority. Both plugins works as expected but removes the other package versions. I am able to execute yum install y, but unable to execute yum install x afterwards. I should be able to execute both repositories in one server. Could you please suggest me, how to achieve this in yum? I have to implement it in server.