South Brother is a mountain in Baxter State Park in Piscataquis County, Maine, standing between Mount Coe and North Brother and forming with North Brother the pair called The Brothers. It lies within the Penobscot River watershed, with its northeastern and southeastern slopes draining through the Klondike into Wassataquoik Stream and the East Branch, while its western side drains by Roaring Brook and Nesowadnehunk Stream to the West Branch. Located about 5 miles from Mount Katahdin, where the Appalachian Trail ends, South Brother stands near one of Maine’s most important mountain landscapes.