Here is what I notice about Phillips surname in Jefferson Township, Ross County, Ohio between 1830 and 1850 census':
1830 - Joseph Phillips 1840 - Joseph Phillips; Samuel Phillips; John Phillips (who moved there c.1837 after leaving McArthur and Elk Township in Athens Co. where he had lived for at least 30 years); Curtis Phillips; & Thomas Phillips 1850 - NONE: all gone
In the 1840 census, the roll is listed in following order: Joseph Phillips, then John Phillips, then Jeremiah Stewart, and then Curtis Phillips.
Joseph (born between 1800 and 1810) may have been a son of John (born between 1770 and 1780). A Joseph Phillips married in Athens County on 8 March 1830 Polly Phillips.
Jeremiah Stewart was born between 1770 and 1780 in Maryland. He was a early settler in Jackson Township, Pike County, Ohio as he appears in the census' for that place in the years 1820 and 1830. His daughter, Jemima (Jermina) married on 19 Feb. 1833 in Pike Co., Curtis Phillips. Jemima was born between 1815 and 1817 in Pike County; Curtis was born in 1804 or 1805 in Scioto County, Ohio. Two of their ten or twelve children at least were born in Ross County: Henry Phillips (15 June 1837 to 9 June 1909) and Curtis B. Phillips (28 Oct. 1841 to 30 March 1921). In 1850 the Curtis Phillips family were living in Lick, Jackson Co., Ohio; in 1860 they were in Fayette Co., Ohio; in the 1870 census for Ohio Curtis is spelled Curtice Phillips. Curtis died sometime between 1870 and 1880. In 1880 his widow Jemima and three of her children (Joseph, Margaret, and Sarah), son-in-law Martin Myers who was a widower then (wife was Catharine Phillips who died c.1879), and various Phillips and Myers grandchildren were all living in Hamilton Township, Franklin County, Ohio. Jemima died after that year at some point.
A possible connexion between Joseph Phillips and Curtis Phillips could be through Thomas Phillips and his wife Polly McDowell who were married on 15 Feb. 1804 in Harrison, Kentucky. Soon after they were married they moved to Scioto County, Ohio; they may have been the parents of Curtis? Thomas and Polly also had a connexion to Pike Co. They may have also had a son named Benjamin and a daughter also named Polly.
A Benjamin Phillips married Nancy Martin on 30 Oct. 1831 in Pike County. She was the daughter of George (died 1830) and Jane Martin of Washington Twp, Jackson Co., Ohio. Benjamin and Nancy had one child: Thomas. Nancy was dead by March of 1841. I think this Benjamin (1850 census says he was born in Ohio in 1800) may have remarried to a Sarah moving to Polk County, Iowa, and had more children there.
As state above a Polly Phillips married Joseph Phillips in Pike Co. in 1830. She may have been a daughter of Thomas and Polly (McDowell) Phillips?
Whew, just putting out various information to see if all these above Phillips are somehow related.