Re. Thomas Corlett's 6-yr-old grandson in the 1891 census, named as George H Gilmour, I'm still puzzling as to where he could fit in. Does this mean that Thomas had three marriages? Or an illegitimate daughter. And he was only born c.1857, according to the 1891 census.

BL's birth registrations have this entry:
George GILMOUR, b.2 Oct 1884, Lonan, [Father:] Not given, [Mother:] Elizabeth GILMOUR. [An illegitimate birth.]

This is Thomas's first? marriage, from FamilySearch:
name: Thomas Corlett
event: Marriage
event date: 14 Aug 1879
event place: Arbory, Isle of Man
gender: Male
marital status: Single
father: Philip Corlett
spouse: Mary Kinvig
spouse's marital status: Single
spouse's father: Richard Kinvig
digital folder number: 004499877

Thomas Corlett's baptism: 30 Jul 1856 Patrick,​ Isle of Man
Parents: Philip Corlet,​ Ann

Possibly:
Phil Corlett & Anne Skinner

name: Philip Corlett
event: Marriage
event date: 14 Nov 1840
event place: Patrick, Isle of Man
gender: Male
marital status: Single
father: Phil Corlett
spouse: Anne Skinner
spouse's marital status: Single
spouse's father: John Skinner
digital folder number: 004494342

Mary Kinvig's baptism:
name: Mary Kinvig event: Christening
event date: 01 Nov 1857
event place: Arbory, Isle of Man
gender: Female
father: Richard Kinvig
mother: Ann Elliott
digital folder number: 004499802

Richard & Ann Elliott married 09 Feb 1839 Arbory [IGI].

To get other IGI records for the IOM see: www.familysearch.org and choose Isle of Man.

For other index entries by Brian Lawson see: www.iomfhs.im/lawsons/LawsonBMD/Main_Site_index.html

Sue