Complex sentence: Her younger brother, Michael, is an ultimate pest and seizes any opportunity to aggravate and annoy his sister, and her older brother, Chad, seems to do nothing to dissuade Michael from irritating Stevie.
Split into simpler sentences: Her younger brother Michael, is the ultimate pest and seizes any opportunity to aggravate and annoy his sister. Stevie's older brother, Chad does nothing to dissuade Michael from irritating Stevie.