I want to have multiple streams (up to 4) on one YouTube Live broadcast, Is that possible?
you can use something like a M/E switcher with a multiviewer to do this. Just feed the program out into the computer you are streaming from using an input card.

I have not used youtube streaming, but I know that justin.tv or other streaming services can use something like OBS to switch between scenes which you can setup with different video inputs in different configurations on the stream.

As these all rely on having external gear to get the camera feeds to the streaming location, the google hangout solution would be the best, as I am assuming you are on a low budget