A few further thoughts....
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There is a Jane Trahar age 2, niece living with the Schwarman family in 1851. She must be related to Edward.
From GRO
Birth reg TRAHAR, JANE ELIZABETH mother maiden name TRAHAR
GRO Reference: 1848 D Quarter in SAINT GEORGE (IN THE EAST) Volume 02 Page 116
https://www.gro.gov.uk/gro/content/certificates/login.aspThis would seem to be the Jane Elizabeth chr at St John the Baptist Hoxton Middlesex on 22 Jan 1862, dob 22 Sept 1848, daughter of John, deceased Mariner and Mary Ann. (Gut feeling is John is a made up father)
Might be worth investing in her birth cert to see who Mary Ann Trahar was.
The witnesses at the 1827 marriage to Jane Underwood, were Elizabeth JAMES and John Wheeler.
An Elizabeth Trahar married William JAMES on 6 may 1823 at Saint George The Martyr: Borough High Street, Southwark. Witnesses William Stevens, Temperance Stevens. I think the Stevens were a married couple as there are a few baptisms to a pair of this name in Southwark. William was a hair dresser. Temperance was nee Williams. May just have been family friends.