there was an earlier Peter bur 1743 - the birth I've noted as Jan 1742 if however this was actually 1741 in reg and then wrongly assumed to be 1741/2 then this son Peter would be alive for a will written just before gfa Peter's death

however should point out that there were Peter Corkill's in Braddan from 1701 so are you sure of fam linkage

Patrick Corkill acquired Ballacreggan (abbey land) pre 1704 by marriage to Jane Cubbon in 1702