The minimum area of any lot or parcel of land in the Low Density Residential PRO zone designated for one-family dwellings shall have an area of not less than four thousand five hundred (4,500) square feet and lots designated for twin homes shall have an area of not less than four thousand (4,000) square feet, unless otherwise approved by the Planning Commission. Because twin homes are attached on a common lot line, dwellings shall be designed and built in pairs with one unit on each lot.