Bernard Yoak is the son of Lloyd Yoak, who is the son of Isaac Yoak, who is the son of Elias Yoak ( My line is from Elias' 2nd marriage while yours is from the first) and Elias is the son of John Yoak who emmigrated from Germany abt. 1770. So far no one has been able to find anything further back than that. Hope this helps you getting started.
Your 1/2 Cousin,
Jeff