Hi JAP,
I don't know if Armstrong and Agnes had any children or not, and its possible that young Armstrong who died in 1924 was related, if so then he would probably have been a grandson, as you said the name is an unusual one.
Armstrong appears twice on the 1881 Census for some reason, the details are as follows:
1881 Census
3 West Marsh, Paisley aged 27 Armstrong McAuley Shoemaker
3 West Marsh, Paisley aged 21 Agnes McAuley
3 West Marsh, Paisley aged 20 Sarah Muldoon (lodger)
1881 Census
Dwelling: 75 High Street Esther CAMPBELL Boarder N/A 14 F Ireland
Dwelling: 75 High Street Maryann MC AULEY Wife Married 55 F Ireland
Dwelling: 75 High Street Thomas MC AULEY Head Married 66 M Labourer Water Coy Ireland
Dwelling: 75 High Street Armstrong MC AULEY Son Married 26 M Shoemaker Greenock, Renfrew, Scotland
Dwelling: 75 High Street Margaret MC AULEY Daughter N/A 11 F Scholar Paisley, Renfrew, Scotland
For some reason Armstrong's mothers name has been transcribed as Maryann instead of Fanny or Frances.
Best wishes
Gwyn
