My mother Dorothy (83 born in Cardiff) was an Organ before she married my Dad. I have recently started researching the Organ family tree and I believe that my great grandfather David Organ was younger brother (by about 2 years) to the Samuel Organ you are seeking.
If I am correct "Your" Samuel Organ was married to Mary Organ (born in Newport, 36 at the time of the 1881 Census living in 4 Cecil St., Roath Cardiff with 5 children Eliza J Organ 13, Mary E.Organ 9, Kate G.Organ (7), Samuel H.Organ (5) and Sarah A. Organ (10m).
I say "your" Samuel because my Grandfather, David's son was Samuel Hadley Organ born in 1885.
The 1881 Census notes "your" Samuel and "my" David as Carpenters. David eventually moved on to being a self employed Market Gardener.
I'd love to receive verification that we have a family link! If so have you made any progress researching father back than 1851, North Nibley.