Streaming live to co-hosts
You need your own stream server.  The problem with services like YouTube and Twitch.TV is that your stream has to go through a lot of processing and content distribution on their end before it goes out to viewers.  That processing takes time and results in lag.  You can send the exact same stream to your own stream server and have it directly related with far FAR less delay (sub-second to a couple seconds), but are limited to the capabilities of your stream server to meet demand.

I've only done this kind of thing with Windows Expression Encoder in the past using a Windows Media Streaming server which is pretty easy to use, but only works on WMV files and thus isn't really all that good of a modern solution for h.264 video in cross platform streams.  RED5 should theoretically be capable of relaying a stream for you and you could either set it up locally or preferably throw it up on a VPS somewhere that can do the relaying for you (as 16mbit will get consumed really fast sending a 4.5mbps stream to multiple people).

Streaming is unfortunately not particularly easy to get setup and going for yourself though and that is a big part of why services that simplify it, like Youtube and Twitch.TV, are so popular despite their massive lag times.