Kay,
I've tracked 2 families in 1861 - 1881 but won't do any more unless you recognise the names of one of them.
1861 95 Malew Street, C'town.

J.K. 38, Mason, b.C'town.

Margaret, 49, b. Michael

Margaret, 9, b. C'town.

1871 42 Malew Street, C't.

John, 47. Stonemason

Margaret 55 Mason's wife, b. K. Michael

Margaret 19, Dressmaker, b. C't.

1881 33 Malew Street

John 59 Builder empl. 2 men

Margaret 68, b. Michael

Margaret Fargher 29 Dau.

John Fargher 28, Son-in-law, Cabinet maker, b. Douglas

Margaret 2 + Annie 6 mos. (Fargher)

2nd family:

1861 65 Malew Street
John 36 (?) Painter
Jane 36
John 12
James 10
Robert 7
Joseph 5
Margaret 3
Philip 1

1871 8 Mill Street
John 48 Journeyman Painter, B. C't
Jane 44, b Marown
Joseph 15 App. Painter b. C't
Margaret 12 Scholar b. C't
Philip 10 Scholar b. C't
Anne 8 Scholar b. C't
Thomas, 5 b. C't
Evan 2 b. C't
Henry 2m b. C't

1881 47 Queen Sreet

John K. 57 Painter
Jane 55
Thomas 15 Painter
Evan 11

Given the name Thomas in this family, there must be a connection with Robert's family in 1851, even though this John is a Painter, not a Mason. It was common for people to call children after cousins and uncles etc. though.

Hope this may help. It's better to do this working backwards so you know who you're looking for!
Jo