I now have a copy of Shepard Barclay's biography. Privately published in St. Louis in 1931, the book appears to have been edited by William L. R. Gifford. The biographical sketch was prepared by Clarence E. Miller and the book also includes a brief essay on Barclay's legal career written by S. Mayner Wallace. The primary source for the biography was Barclay's private papers. The book was written at the request of Edward Mallinckrodt, Barclay's nephew, "(in) affectionate remembrance of a long and happy relationship."
A couple of interesting things:
-With regards to Barclay's parentage, there appears to be a reason why it wasn't mentioned in other sources. It's a bit complicated and a tad scandalous. Shepard Barclay was born on November 3, 1847 to Britton Armstrong Hill and Mary Shepard Hill. Britton Armstrong Hill was a lawyer from New York who had come to St. Louis in 1841 and married Elihu Shepard's daughter on October 8, 1845. The marriage was not a happy one and ended on March 2, 1849 when the two were divorced "by act of the state legislature." On June 26, 1854, Mary Shepard married David Robert Barclay, a lawyer and native of Pennsylvania, who had moved to St. Louis in 1850.
-While he was known as Shepard Barclay to his teachers and friends, the man's legal name was actually Shepard Hill. In 1868, "upon reaching his majority," he had his name legally changed from Hill to Barclay.
-There are a couple of references to baseball in the book although not much in the way of detail. Miller quotes Barclay with regards to his days at St. Louis University as saying that "(in) 1867, the year of my graduation, we held the local college championship in base ball, after a great game with our leading rival in St. Louis." This game is most likely the one between SLU and Washington University that Kelsoe wrote about in his book. There is also a reference to Barclay enjoying athletics and the outdoors and as someone who had a lifelong love of baseball. There is no mention of his having played baseball at the University of Virginia or in Europe. There also is no mention of the Union Club.
-Of the top of my head, I can't imagine Barclay having played that much with the Union Club or having been a rather prominent member. I can't imagine him playing with the club in 1860 when he was 12 or 13 and Kelsoe wrote that Barclay pitched for SLU before joining the club. So based on that, Barclay most likely didn't join the Union Club until 1867. In December of 1869, he left for Europe and would not return home until May of 1872, by which time the Union Club had stopped playing baseball. At best, if Kelsoe is correct and Barclay didn't join the club until after he graduated from SLU, Shepard Barclay was a playing member of the Union Club for two years.