From a distance, it's difficult to find anything about your father's half-siblings. All I know about your father is from your posts and an obituary at FindAGrave.com.
Any other children of Samuel or Leona might still be alive, so their vitals are not likely to be found online for privacy reasons.
One possibility is the Pocahontas County Court House. When Samuel died, the death certificate showed that he was normally a resident of Huntersville and that he was married, though no spouse was named. There may be records in Marlinton that name Samuel's wife or children.