The 2020 census found 4,249 people in the township.

Located in the southern part of the county, it borders the following townships: Three incorporated villages are located in Twin Township: Statewide, other Twin Townships are located in Preble and Ross counties.

[4] The township takes its name from Twin Creek.

[5] The township is governed by a three-member board of trustees, who are elected in November of odd-numbered years to a four-year term beginning on the following January 1.

There is also an elected township fiscal officer,[6] who serves a four-year term beginning on April 1 of the year after the election, which is held in November of the year before the presidential election.