It’s possible that William was married three times. If so, Margaret Conaway died in 1900.

William may be William Piersol Dean Kelley, b. March 2, 1870, in Grindstone, Fayette Co, PA. according to a forum post on ancestry.com. The same poster suggested he may have married a Mary Jane Black on March 27, 1901.

1900 Census, Redstone Twp., Fayette Co., PA
Kelley, William, head, 31, b. Mar 1869, m. 4 yrs., b. PA, parents b. PA, railroad laborer
Margaret, wife, 43, b. Jul 1856, m. 4 yrs., 0 children, b. PA, parents b. PA

1910 Census, Menallen Twp., Fayette Co., PA, April 28, 1910
Kelley, Wililam P., head, 39, widowed, b. PA, parents b. PA, laborer, public works
Wayne H., son, 5, b. PA, parents b. PA
Emma M., dau., 3, b. PA, parents b. PA

In the 1920 census, William was widowed and living with his son Wayne in his brother Searight’s household in Union Twp., Washingnton Co., PA (see Searight for details).