In 1887 David, his parents and siblings were living in Whitman Co., Washington Territory.
In 1883, they were still living in Whitman County, Washington Terr.
A male was born to D. P. Posey and Belle Sowels? Sorrels? in Pullman, WA on July 23, 1906.
In 1910 [David] Ira, Belle, Bessie and Raymond Posey were living in Palouse, Whitman Co., WA.
An Irene M. Posey b. 26 Oct 1917 Franklin Co to David I. Posey and Belle Sarles. Source: Washington Birth Index 1907-19, Ancestry.
On Sept. 12, 1918 David Ila Posey was living at B St., Pasco, Franklin Co., WA. Born=14 Sept. 1881. Occupation=Drayman for Horrigan Bros., Horrygan Bev Store, Pasco. Wife=Bell Posey, wife, Pasco. Source: World War I Draft Registration Cards 1917-18, Ancestry.
In 1920 the family was still living in Pasco.
David I. Posey, b. KS, 37 yrs old, drayman.
Bell, wife, b. NE, 34.
Bessie, b. WA, 15.
Raymond, b. WA, 13.
Verne, b. WA, 4 6/12ths.
Irene M., b. WA, 2 3/12ths.
I'd look in Franklin Co. for Bessie's marriage info. Contact the Franklin County auditor and ask if they will look through 1920 to 1930. If they won't, contact Random Acts Genealogical Kindness. After on the site, read guidelines, choose Washington, choose Franklin.
For info on how to request a copy of David's death certificate, see Center for Health Statistics, www.doh.wa.gov/EHSPHL/CHS/cert.htm .
In 1930 most of the family was living in Pasco.
Belle L. Poesy, b. NE, 43, widow, no occupation shown.
Berne [Verne?] D., b. WA, 14.
Marian M., b. WA, 11.
Allen M., b. WA, 8.
Albert Schott, roomer.
A Belle Lovinda Poesy, 73 years old, died 28 Jan 1960, Pasco, Franklin Co., WA. Father's Name=Sorles. Mother's Name=Lucinda. Source: Washington Death Index, Washington State Digital Archives.
You can request an obituary for Belle from Random Acts Genealogical Kindness or the Washington State Library.
A Verne D Posey born Aug. 29, 1915 died April 30, 1974, place unknown. Source: Social Security Death Index, Washington State Digital Archives. Successful Searching!