Hi Peter,
I have the image from Family Search of the specific marriage from Braddan Marriages 1725 [1725/26] taken from Page 143 of 160 pages. However, I don't know how to paste an image into here. You can go into FS yourself to find it.

As you say, it leaves out the surname “Kewley”. He was from an Onchan family, so perhaps wasn’t known by the Braddan parish clerk.

I had said “know quite a bit” which is rather presumptious of me. I was just glad to get away from all the Johns, and to have a much rarer first name to work with for a change.

Though the surname is missing, I’m comfortable it’s Gilbert Kewley. The children of Gilbert Kewley start appearing very quickly in the Braddan register ( just 1 month for #1 Esther). Gilbert’s mother Margaret McYlroy [prev Kewley] als Corkill’s Braddan 1735 will mentions (after eldest ch Wm Kewley of Onchan) ch Gilbert + wife KK Braddan plus Esther Kewley who must be the granddaughter. The mother was buried in Onchan, where her elder son William lived and where her first husband John Kewley was buried (1710, mentioned wife, 3 ch Wm Gilbert & John).

Gilbert and Joney’s 1771 and 1779 wills match well, posted below.
MNB Braddan:
1771-2 A 38 KEWLEY Gilbert d 17 apr 1771;gson john corrin;son robt;names danl colvin;gdau jane corrin;son-i-l james corrin + dau jane; [EG note: "dau jane" s/b "dau mary"?]

1779-1 A 8 KEWLEY Joney corlett d 3 mar 1779;son robt;niece jane quine als corrin;son [?in-law] james corrin+wife dau mary als kewley exors

Gilbert is mentioned below as an uncle of these Cannell children. I think the decedent Eliz Cannell als Corlet must be a sister of Gilbert’s wife Joney Corlett, and the other uncle Thomas Corlett is likely a brother. I haven’t researched them.
MNB Braddan:
1741-1 E d CANNELL Elizabeth corlet d beg mar 1740/1;ch robt,elinor,ann all ua uncle thos corlet + gilbt kewley;pledges wm quirk taylor,christopher kinley;husb wm;inv

To be honest, I’m not 100% positive that the Robert Kewley who married Ann Clark 1760 Braddan is the Robert b 1731 s/o Gilbert and Joney. I give it a 95 though. Evidence in favour includes knowing G&J’s son lived to a least 1779 (wills), their first daughter named Joney, first son Robert. Witnesses to the 12 July 1760 Braddan marriage were David Moore and John Kewley. The signature for the witness John Kewley is identical to the groom in the next marriage, 26 July 1760, of John Kewley to Margaret Corlet. John Kewley is from the Ballanard Onchan family. Wife Margaret died 1766 and he remarried to Elizabeth Cannell 13 Jan 1767. I wonder if there is a connection between the Ballanard Kewleys and the Black Quarter Kewleys?

I hope this helps you.