David Dennison's wife was Mary Ann Douglass. They had seven children, James D, John (mar. Jan Morehead) , Huston, Wiley (my gggg-grandfather), Jane, Malinda, and Nancy.
David did have brothers and sisters. I off hand know of Thomas, James, and possibly William. Thomas, David, James were born in Augusta Co. VA in the mid-late 1700. Augusta Co VA in mid 1700's was what now is KY. They owned land adjacent to each other in Bourbon Co KY and lived near Daniel and William Dennison. Bourbon Co. KY was formed from Augusta Co VA, then Kentucky Co VA, and then Fayette Co. In about 1790 David and Thomas married sisters and move to Madison Co. Ohio in the early 1800's.
David's father was possibly Daniel Denniston (II or III) of Augusta (later Rockingham VA) and a possible grandson or g-grandson of Daniel Denniston (I). Daniel Denniston (I) came for Ireland some time in the early 1700's with Wife Sarah, daughter Ann and possible Daniel (II). His died about 1749 and a will exists.
What part of the John Dennison family tree are you from? I know of 4 of his children James W, Burr Wright, Milton White, and Jane.
I have more info but for now I hope this helps. My email is firstname.lastname@example.org
and I would like to discuss it further via email.
Please feel free to contact me.