Is it possile to have two separate MQTT brokers in HA (no bridge)?

I have two groups of MQTT clients. I want them to exchange messages through MQTT broker but only within each group, meaning, client connected to one broker should not be able to see or send messages to other group.

At the same time, HA should see both brokers and clients so it can monitor them or introduce some automations involving both groups.

Is this possible?

Al I can find is related to having two brokers and bridging them to allow messages to pass through.