I have new requirement in Oracle replication

There are two site A and B. In each site, there are two databases. All the data in four databases should synchronized in any time. DB1 and DB2 are in site A. DB3 and DB 4 in the site B

I set multi-master replication between DB1<->DB2. Here I created maser group in DB1
Then I set the multi-master replication between DB3<->DB2. Here I created master group in DB3


I made an insert in DB1. It update the DB2 but not in the DB3.
I made an insert in DB3, It updates only in the DB2.
I made an insert in DB2, it updates both DB3 and DB1.

Can anyone please help me to setup the replication, so the update made in the DB 1 update DB2 and then DB3?


Regards,
Bala chander