I have never done any research for Cumberland County, but I have for other North Carolina Counties. Most of the marriages of Free people were done the same way as the rest of the citizenry of each county. There are Marriage Bonds that exist from 1741 - 1868 for North Carolina, and after that there are Marriage licenses/ and or Marriage Registers, where marriages were recorded for people of all races. There were marriages for some Free People of Color made after the Civil War which did get recorded separately because they were mostly freed slaves having their marriages registered with the Counties as the law required them to do, and are referred to as Cohabitation Records. If your family was indeed free prior to the Civil War, there should be some record of their marriages in either the bonds or at the County Courthouses. There are also microfilms of the marriages in North Carolina which you could look through, available thru your local Family History Centers, as well as the North Carolina State Archives.