As for the children of the theoretical two wives of Irish founder Hugh Abernathy, my files show three children (James, Nancy Mrs Rushing, & Jane Mrs Morrow) nicely sandwiched between William (cir 1795) and Isabel (cir 1788).
Caveat: this is not my branch. My Abernathy ancestress descended from the Robert Abernathy of Charles City County VA (cir 1632-1685), and I am much more familiar with that line.
I cannot recall which Abernathy I corresponded with from that particular Irish branch who first suggested two wives to me as a solution to the span of births over such a long period. It's certainly possible, of course.
As for the LDS site I've seen records on the site giving multiple wives for many individuals who, when properly researched, cannot AT ALL support such a contention.
Besides, that site shows that I died in a community I haven't set foot in since I left it, barely out of kinder-garden, in 1946!!!