Need to configure Availability Groups between three different SQL failover instance

We have total 6 Nodes and 3 failover cluster (Each with two node). - Cluster1.TestAD.com(Node1,Node2) - SQL Failover Instance (SQL1) - 1 TB Shared storage - Cluster2.TestAD.com(Node3,Node4) - SQL Failover Instance (SQL2)- 1 TB Shared storage - Cluster3.TestAD.com(Node5,Node6) - SQL Failover Instance (SQL3)- 1 TB Shared storage Now we want to create availability group setup between above three SQL instance. We plan to create new cluster (cluster4.TestAD.com ) with all six node and create Availability groups with all three instance. SQL Edition : SQL Server 2012 R2 Enterprise Is it possible? Any other recommendations ?