replica volumes can be build only from 2 or 3 bricks. There is no way to make a replica volume from a 4 bricks.

But you may combine distributed volumes and replica volumes [1]:

gluster volume create test-volume replica 2 transport tcp server1:/b1 server2:/b2 server3:/b3 server4:/b4

test-volume would be like a RAID10 - you will have two replica volumes b1+b2 and b3+b4 combined into a single distributed volume. In that case you will
have only two copies of your data. Part of your data will be stored twice on b1 and b2 and another one part will be stored twice at b3 and b4
You will be able to extend that distributed volume by adding new replicas.

[1] https://gluster.readthedocs.io/en/latest/Administrator%20Guide/Setting%20Up%20Volumes/#creating-distributed-replicated-volumes