I don't know that they're even related, but I found it interesting that the people you're looking for went to Montana. My great-grandmother, Frances (Polic or Polich) Stoken/Stoken was from Hreljin, Croatia. She was the daughter of Joannes and Maria Polic, per Hreljin's birth records. She came to the US in 1906, and joined her husband, Matt Stokan in Butte. They ended up leaving Butte about 1914, when her husband was kicked out of the mines for "black lung." They went to Lincoln Co., MT where they homesteaded. John Vukonich (1874-1947) and his family were also from Croatia (kin?) and went up with them. It has been said they were going to join forces and have a big ranch named Black Hawk or something, but it was alleged that since Matt couldn't read/write in English he apparently accused John Vukonich of not being forthcoming or something, so they ended up getting their homesteads individually. John and Helen Vukonich had a son, John W. Vukonich (1907-1994) who married Helen Tripp, and she died in 2008.