I have found very little on this couple; nothing past 1860. I have not seen the actual 1860 census and do not have any children for the couple. According to the info on the Mormon's site, William Stinnett died in Hill Co., Texas, but I am unable to confirm that at the moment.
It is most confusing since there are two Harriett's enumerated with the parents John Yearout and Martha Roulston in the 1850 census. Martha (Yearout) and her husband Samuel Stinnett are residing next to her parents in 1850. Her older sister Susan Yearout is also listed as being home. Susan suposedly married Mr. Cupp in 1846, but there are other marriages for a Susan Yearout in the 1850's. I am beginning to wonder if their mother, Mrs. Martha Yearout, just listed all her children in 1850 even if they were no longer living at home.
I am curious to know the relationship between Samuel and William Stinnett. I do not believe they are brothers; perhaps cousins?