my great-grandfather John Burnham Eaton married ELIZABETH ROSE ALLEN. In the 1850 census I found the couple in Cincinnati, living with a Cynthia Brooks—apparently a widow who took in boarders—and two young men, JOSEPH and WILLIAM ALLEN, who are probably Elizabeth's brothers.Elizabeth is 27, born in Ohio. Joseph is 20, also born in Ohio. William is 29, born in New York.Is this trio of siblings familiar to you from your family tree?
Because the oldest was born in New York, I'd guess that this Allen family moved from NY to Ohio between 1821 and 1830.