This is probably George Ovenden.
With his wife and family - so mot free to marry Rachael. Presumably kept her as a mistress, either leadinf a double life, or with his wifes knowledge
1871
79 Guilford Street, St Pancras
George Ovenden 40 surveyor bn Middlesex
Anna M 40 wife bn Bedford
George C 19 bn Hackney
William 16 bn Kensington
Henry 14 bn Kensington
Edward 13 bn Holborn
Charles 11 bn Paddington
MAry Swannell? 24 sister in law annuitant bn Bedford
Charlotte Reeling general servant
So the George Ovenden, witnessing the marriage, could be Georginas half brother, if the two families were in contact?