Thank you for your suggestions. I need to make a trip to the courthouse in Uniontown for more than one family.
After I posted this, I followed up on a clue from an April 1941 Uniontown newspaper article I found online that said Clarence's brother John died in Morgantown, West Virginia. I went to the West Virginia Vital Records website which gave me brother John Michael Hixenbaugh's actual death certificate. It lists John Henry Hixenbaugh, born Fayette City, as his father and Ella McMenar, born in Ohio, as his mother. I then found John Michael Hixenbaugh in the 1920 census in Grafton, Taylor, West Virginia and his father was also living as a boarder and glass blower in Grafton. In 1930 John Michael is living in Morgantown and I was able to add brother James, born in 1898 in Pennsylvania, who was living in John's household, so now I have two siblings for Clarence.
The father John Henry Hixenbaugh's death certificate is also online at West Virginia Vital Records. He was born 7 July 1864, Fayette City, to John and (Hannah)Rebecca West Hixenbaugh and he died 9 October 1936 in Grafton, Taylor, West Virginia. I then found him in the 1870, 1880, 1920 and 1930 census. The 1900 and 1910 census is still missing! I have not yet found Ella in any census and I'm not sure that McMenar is the correct spelling of her last name. Ella had died by 1920 when John Henry is listed as a widower.