I was watching my boxset 10 last night and they did the episode where [spoiler]Barnabas, Julia and Stokes conspire to break in to Blair House to kill Eve. While Barny's off actually getting munched on by Angelique[/spoiler]Stokes regales Nicholas w/stories of the Old House history and he begins by telling him that the Old House was built in 1767 as a wedding present to Naomi from Joshua.
So, if we assume that they had Barnabas right away, that would make his birth year 1768 and him 28, or about to turn 28 depending on the month of his birth, when he "died" in 1796. Hmmm, Frid was 43 during that plotline, in fact they actually celebrated his birthday during it (see My Scrapbook Memories of DS for pics) and although he was a youthful looking 43, I personally don't think he looked 28! 33, *maybe*, but 28....? Think this was a big continuity blooper!