Just found an 1871 census entry (in Brecknock) with the largest generational difference I've seen yet. Uriah Evans, age 98 yrs, with wife Mary, age 28 yrs, and son John, 2 yrs. They appear to have married in 1866 and son John was born 1868 (i.e. not born before marriage or Mary already pregnant when married).
Uriah is living next door to sons Daniel (age 52 yrs) and Samuel (age 45 yrs) by his first marriage.
Admittedly Uriah's YOB meanders between censuses (as well as 1773 there's also 1772, 1781 and 1791) but it still makes me wonder how it may impact on DNA analysis given it's possible for someone still alive to have a great grandfather born in the 1770/80s. Or if son John repeated his father's trend, even a grandfather born this far back
