what do ushers do?

and where do they sit during the ceremony?

i need an excuse to get my brothers in a tux but i am only having 2 people in my BP.

They can walk people down the aisle to their seats (i.e. grandma) They can hand out programs if you're not putting them on chairs and they can seat guests at RH or sit at the escort card table to help...pretty much whatever you need them to do and they can sit anywhere in the ceremony, in the front, in the back, really up to you. Also, they can do readings in the ceremony or be designated to give a toast...

eta: typos