I am trying to distribute the load balancing between servers connected with three proxies.

In my setup, I have three proxy servers and each of them have two origin servers and one client. 
I would like to balance the load across servers connected with other proxies when the rate of incoming requests are more.
To begin, I started with round robin policy.
First I tried to add the proxy2 and proxy 2 as one of the origin servers in remap config as below: 

map http://UHLB http://UHLB @plugin=balancer.so @pparam=--policy=roundrobin @pparam= @pparam= @pparam= @pparam=
The last two IP addresses are proxy 2 and proxy3.
But It did not work. 
I read about parent proxying. But in my case, I want to load balance. May I please know to configure to achieve load balancing across hierarchical proxies.