All sorts of possibilities with this one. Could he have been Sarah's son? If the father recognised him and put his name on the birth certificate it would have made his surname different from the mother's. A nursling would, I expect, a new-ish baby still being cared for, perhaps he was sickly?
Or, he could have been a neighbours child who was being looked after while the parents worked?
I notice there is a family at 16 Steel St by the name of Lochrine. Also another family at Scotts Rows, a short distance from Steel St, by the name of Lochrane. This last family had a child aged 1 year, perhaps this John is an older brother?
There is a family in Hamilton in 1891 by the name of Lochren, the mother has young children, she is Mary aged 33 born Wishaw. could she be a sister of Sarah?
Sames goes for the family at Scotts Rows, the mother is Agnes aged 28 born Wishaw. William & Mary Jane had a daughter named Agnes who died January 1872. Did they have another Agnes soon after that? It would make the age correct.
The only thing to do is check the birth for John Lochran and find out who his parents were.
