Brethren is an unincorporated community and census-designated place in the U.S. state of Michigan. The community is located within Dickson Township, Manistee County, and is in the Northern Lower Peninsula of Michigan. The community had a population of 331 at the 2020 census, down from 410 in 2010. The community is located in the Manistee National Forest, 18 miles northeast of Manistee. Brethren has a post office with ZIP code 49619.