Hi,
n case anyone is still looking, here is one source for jPS's siblings:
http://www.yourislandroutes.com/portuguese/johnphilipsousa.s... It my be of interest to his descendents to know that there are many more cousins out there than they might suspect. John Antonia Souse allegedly was "married" to two women at the same time. He had several children of the second "sife" who adopted the surname Sousae. I am a descendant of that family. The families evidently knew each other well and in the mid-sixties, I attended a family reunion in which members of each sect debated as to which were "legitimate."