AlwaysOn Q: readonly secondary databases from 2 separate instances

Hi,

We have a reporting requirement where we would like up-to-date copies of databases from 2 different instances to be made available on the same, new, reporting server. I would much prefer the databases to be in the same instance to avoid cross-instance queries.

Instance 1 
Databases:
oltp1
oltp2
oltp3

Instance 2 
Databases:
dwh1

New Reporting Instance 
Requirement: Readonly databases from the above 2 instances combined in this instance

Databases:
dwh1
oltp1
oltp2

I am looking at creating Always On Availability Groups as a readonly replica looks good. However I am unsure if the databases from the 2 instances can reside on the same reporting instance, or do they need to reside in separate instances.

Thanks!