sub module branches

Hi

I have a situation like

project/source.git
           /submod_1
           /submod_2

I need to modify code in all 3 repos viz. source, submod_1 & submod_2.

If I create branch in source, will it propogate to remaining
submodules ? or in other words can I have "global branch" and "global
tag"

Thx/

Mahesh.