"Chozno" undoubtedly means either great-great-great-great-grandfather or great-great-great-great-grandson; here, obviously, it's the former.

However, in this case it is not actually true. The José de San Martín who was involved in this "concurso que gestionó Tabanera" is not a descendant of the famous General José de San Martín who crossed the Andes. He can't be, because there are no direct descendants of General San Martín. He had one daughter, Mercedes Tomasa de San Martín y Escalada. She married an Argentine doctor named Mariano Severo Balcarce and had two daughters, Josefa Dominga and María Mercedes Balcarce y San Martín. María Mercedes died unmarried and without issue at 27. Josefa married Eduardo María de los Dolores Gutiérrez de Estrada y Gómez de la Cortina, a Mexican diplomat, but also died without issue, in 1924. Therefore the direct line of General San Martín was extinguished.

http://es.wikipedia.org/wiki/José_de_San_Martín
http://es.wikipedia.org/wiki/Mercedes_Tomasa_San_Martín_y_Es...
http://es.wikipedia.org/wiki/Josefa_Dominga_Balcarce

So really they should have said "tocayo", namesake, rather than "chozno": the two José de San Martíns being compared here are not related; they simply have the same name. However, I have found no evidence that "chozno" can mean "tocayo". Either the author thinks mistakenly that one was descended from the other, or he/she is using the term loosely. Either way, I don't feel it should be corrected in the translation, tempting though it is.