In what way? Did they have a 2nd cousin who owned slaves? Did a Great Uncle or Aunt have an in law who owned them? I have seen this 1/3 figure posted, and I think it is bogus. By the same criterea, I could prove that 1/3 of Americans belonged to the SS in WW2.
It is based on the percent of total households just like the rate of home ownership is calculated today.
If you think the numbers are "bogus" you had best let the University of Virginia know that their historicaql census figures are all screwed up.
Here's the way slave ownership broke down by state in the 1860 census.
Census data can be appealed to in order to determine the extent of slave ownership in each of the states that allowed it in 1860. The figures given here are the percentage of slave-owning families as a fraction of total free households in the state. The data was taken from a census archive site at the University of Virginia.
Mississippi: 49% South Carolina: 46% Georgia: 37% Alabama: 35% Florida: 34%
Louisiana: 29% Texas: 28% North Carolina: 28% Virginia: 26% Tennessee: 25%
Kentucky: 23% Arkansas: 20% Missouri: 13% Maryland: 12% Delaware: 3% In the Lower South (SC, GA, AL, MS, LA, TX, FL -- those states that seceded first), about 36.7% of the white families owned slaves. In the Middle South (VA, NC, TN, AR -- those states that seceded only after Fort Sumter was fired on) the percentage is around 25.3%, and the total for the two combined regions -- which is what most folks think of as the Confederacy -- is 30.8%. In the Border States (DE, MD, KY, MO -- those slave states that did not secede) the percentage of slave-ownership was 15.9%, and the total throughout the slave states was almost exactly 26%.