This relates to FamilySearch's amazing experimental full-text search which my cousin tried out a month ago.
Step One. He located a probate from 1839 where the Executor of the will of Robert Mills of Fishkill, Dutchess County, New York was Reuben Miller. Reuben was listing the heirs of the deceased and asking them to appear in the nearby town of Poughkeepsie to process the will. "To all to whom these presents shall come or may concern and especially to George Miller of Canada....more people....Abraham Miller of Fishkill...more people.."
My cousin and I descend from George Miller born in Poughkeepsie in 1809 who moved to Canada around 1830. My DNA matches descendants of Reuben Miller who lived in Poughkeepsie and Abraham Miller who lived in Fishkill, both men remaining in New York until their deaths in the 1880's.
Step Two. I checked FamilySearch under Robert Mills and found an earlier will for his mother (Marcy Mills) who died 10 Dec 1831 in Fishkill, and the probate was processed by Robert Mills and said the following, sworn 7th May 1832 about her heirs: "James, Robert, Reuben, Catharine, Marcy, Abraham, Henry, John and George Miller, grandchildren of the deceased and children of Sarah Miller deceased."
Step Three. Fill in the Mills children. Mercy (Marcy) Mills, born Phillips was in WikiTree and her husband Robert Mills Sr. I added all their children including Sarah (Mills) Miller.
Step Four. Research and more research. Stumbling blocks. Who was Sarah (Mills) Miller's husband? This shows that even established research can have issues. The Settlers of the Beekman Patent has a good account of the Mills Family then adds that perhaps Sarah Mills married James Cable in 1820 and died in 1823 at age 26 because of a newspaper notice. So Sarah Mills, born in 1797, had nine children with some man named Miller, giving birth to Reuben at age 6, and all the rest before marrying James Cable in 1820 under her maiden name? Obviously it's two different women named Sarah Mills. At least the resource said it's not confirmed. Just a maybe.
Step Five. Research. More research. Before adding or connecting. Or changing. Wish me luck as this 40-year brick wall starts to crumble.