I suspect one clue is in the name Peter - this 9+ Dorothy) seemed confined to one branch of the Braddan/Douglas Corkills - I have added a few more Braddan will summaries (only forgetting 1724 Thomas who was almost certainly the tailor and husb of Cath Vinch [Finch] with ch John + Cath as a deed SSS Oct 1739 26 - dated 21 Jun 1739;recites that Thomas Corkill(tailor, Douglas) d 2 Jun 1724 bequeathing half house to dau Cathrine Corkill - also his wife Cath died 4 yrs later thus the house + garden came to their children Cath + John Corkill - to end disputes Cath surrenders to bro John her title to sd house reserving a bed room for herself whilst single
However there is a 1710 will for Margt Corkill als Lewney - [Douglas]d 26 Feb 1710;husb Wm(her part of a cow, colt + flax - a yard of linen for her to be buried in);unnamed - ua children; pledges Thomas Corkill + Wm Kelly;inv £1 7s 6d; 1738: Wm Corkill acks his share of £1 7s + 6d viz 13s 9d from fa Wm Corkill(thus a 2nd child)- m Bra 17071028 so Wm almost certainly remarried but to whom?

also added quite a number more deeds but these are on CD