There is a marriage listed on Lancashire OPC
https://www.lan-opc.org.uk/
12 Oct 1874 Thomas Roberts, mariner to Ann Dixon
Witnesses at the marriage were Walter Roberts, Mary Jane Roberts.
Looking for a census with Thomas born 1848 Manchester with siblings Walter and Mary Jane came up with this one (ROBERTS transcriber as POBERTS on Anc )
1861 census St Thomas Liverpool, 5 Templar Terrace
John Roberts Head 44 born Manchester Mechanic iron and brass bedsteads
Sarah Roberts wife 42 born Manchester
Thomas Roberts son 13 born Manchester - Errand boy grocer
Walter Roberts son 10 born Manchester
Mary J Roberts daughter 7 born Manchester
https://www.familysearch.org/ark:/61903/1:1:M75H-CG6The brother Walter (birth registered 1850)
Walter ROBERTS married 4 July 1872 Liverpool to Julia Kemp WILLIAMS
Thomas and Mary Jane Roberts were witnesses at the marriage
By 1911 census he had 11 children (3 dead)
[ADDED ; Sorry Ladyhawk, I see you posted much of that already. Don't know how I missed it - maybe got distracted when my neighbour started up his chain saw to cut down a tree!]