how many brokers may i connect to a single broker server
If you mean how many Brokers can you configure in a single Broker Server, there is no theoretical limit. However, since all Brokers within a single Broker Server compete for or share certain physical attributes of the Broker Server (such as listening port, RAM, and document storage files), it is not a good practice to configure very many, and the suggested practice is to configure only one Broker per Broker Server in production.
If you mean connections, then the real question is how many brokers can connect to a single broker (if so, look into territories), or perhaps how many IS’s can connect to a single broker (one, unless you write your own Java service broker client.)