The addition of mmn was from my looking at GRO - that doesn't appear on the actual census entry.

15 June 1863 - Christ Church, Doncaster - by Banns
William Sivel Morcombe, 22, bachelor, Engine Fitter. Father: William, Shoemaker
Martha Holmes, 23,
spinster. Father: George, Surveyor
The marriage also took place prior to Lucy's birth in 1864, which I think would rule out Martha being Lucy's mother, apart from Lucy's mother's maiden name was Reynolds.