。
I share a room with my younger brother.
Literal
I [topic-は] little-brother [with-と] together [possessive-の] room [at-で] living-[polite-state-ています].
一緒の ('shared, together-of,' the attributive form of 一緒) modifies 部屋 ('room'). 暮らす ('to live, pass one's days') + ています (polite ongoing). A simple family-living description.