Cason family of Middlesex, London, England

Am searching for parents of Harry Cason b. 1873 of Hackney, Middlesex, London, England. (Sorry, not sure how all the London/Middlesex stuff works)According to his 1900 marriage record to Alice Sythers, his father is William Cason, who was a pipe maker of Homerton.I have found the family w/o Harry in the 1871 Census in Homerton.William's wife is Mary, children: Susannah, Emma, Charles and Sarah Ann.Have also found marriages for Susannah and Emma with Charles and Sarah Ann present at Susannah's 1886 marriage at St. Luke's Church in Hackney to William Davies.
My problem is that I cannot find any of this family in 1881 nor proof that Harry's mother is Mary as the others.Any help and direction would be most gratefully appreciated.Thank you so much.Carolyn Nelson
moreancestors@comcast.net