As far as I know, if the printer says it supports Google Cloud Print you can print directly from your phone without a PC, but you still need internet (hence the "cloud" part) if you want to do it through the Cloud Print app.
But you
can instead connect directly to the printer and print over WiFi Direct without an access point/router or internet, since that model does support WiFi Direct. You might need/want the
Brother app in order to print.
They also have a manual
here with all the details about WiFi Direct. It may be for different models, but the setup process should be the same or close enough.