Blaine Bettinger, The Genetic Genealogist has an interesting entry. He addresses an article in the Evansville Courier Press which has a photograph showing six generations of a family gathered together.
Like Blaine, I never met my mother's, mother's, mother's, father's mother - the relationship illustrated in the photograph from youngest to oldest. However, it would have been even more unlikely for me. Her name was Elizabeth Sliver Denyer, and she lived from 1798 to 1840. She'd have been 171 when I was born.
For that generation of ancestors, the longest living on my mother's side was probably Nancy Vansellas Van Every who lived from 1799-1880. On my father's side it was likely Gitel Slupsky Dudelsack. She immigrated to America along with her children Selig, Yidel and Toba. She died in 1906, still 63 years before I was born, and is buried in St. Louis. (There are several ancestors on both sides from that generation for whom I do not have positive dates)
To get six generations together you need a lot of luck or several teenage pregnancies. (Assuming every birth at age 20, you still need the eldest to live to 100)
Who is the oldest relative I recall? There are actually two questions there - eldest by age, and eldest by generation.
Israel David Newmark (April 1903 - October 2004). Born in London, England, he was my great grandfather Barney Newmark's youngest brother. However, Israel was born two years prior to his first nephew. Since he was basically the same age, he became known to his nephews and nieces as Uncle Buddy.
Bertha (Cruvant) Newmark (Sept 1886 - June 1978). My great grandmother. I was only 9 years old when she died, but I remember her well. She was truly of that generation.
It is believed she was born in St. Louis, Missouri, though she doesn't appear in the city birth registers, and her father doesn't appear in the city directories until 1890. Family immigration may have occurred anywhere between 1876 and 1885 according to census figures. So exactly where the family was before 1890 isn't certain - we suspect they were in St. Louis, or nearby.