Mr Percy Onward Vandeventer was born in St Louis, Missouri on 29 March 1873. He was the son of Kentucky-born boilermaker Silas C. Vandeventer and the former Margaret Cowell, a native of the Isle of Man. He had an elder sister, Maud. 

Percy, who was involved in the insurance business, was married in September 1897 to Marie E. Scherer (b. 1876), a native of Colorado; for a time the couple lived in St Clair, Illinois but the childless couple apparently later divorced.

In mid-1911 Vandeventer resigned from his post as Missouri agent of Dubuque Fire, intending to spend the next few months travelling, after which he would re-enter the insurance business. Vandeventer, a resident of 3968 Morgan Street in St Louis, was a first cabin passenger aboard the Carpathia when it rescued the survivors of the Titanic disaster; he was travelling with his widowed mother and his sister Maud Huber on a pleasure trip to Europe and they continued on with their vacation after the survivors had been landed in New York. 

Percy was remarried to Margurite Zeller (b. 1898 in St Louis), with whom he had a son named Cowell (b. 1923) and the family moved to Arizona and later California.

Widowed in 1932, Percy Vandeventer returned to Missouri where he died on 22 June 1935. He is buried in a family plot in Bellefontaine Cemetery.