Sarah Singery had a sister Mary Singery (Singrey) married to Daniel Vanbuskirk. My guess is that Rufus Vanbuskirk is the son of Daniel and Mary Singery Vanbuskirk, which is why Rufus refers to Joshua Patterson as cousin. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.