Migrating SQL Cluster Between Inter Forest and Intra-Forest

Hi Experts,

We are in process of Active Directory migration and consolidation activity. We have approx 4 SQL clusters(diffrent forests and diffrent domains in same forest)

Now we need to migrate all SQL cluster to one Domain. All are SQL SERVER 2005-ENT.

Is there any possibility? If yes please help me to  get a detailed ref link/document.

Regards Suman B. Singh