Rob, I suspect the 21 Oct 1838 Marown IGI baptism of Robert Corkill to "Robert Corkill" & Margaret Quirk is wrong, and the father should be "William Corkill". I haven't looked thoroughly but there doesn't seem to be a couple named Robert Corkill & Margaret Quirk (no marriage, no other children). I've seen the error several times where the son's name (in this case "Robert") gets carried over into the father's name, either in the original record or by the transcribers.

Robert's baptism fits nicely between his next older (1836) and younger (1840) siblings and he is with his family in the 1841-1861 census's. I'd go with William Corkill as his father.