Family search shows:Margaret Duncan, b. 3-8-1863, CarnwathDavid, b. 5-6-1867, CambusnethanJames, b. 26-8-1869, CarnwathIsabella, b. 29-8-1872, Cambusnethan
Their marriage being in the 1850s just seems a bit odd.
Possibly James and Isabella's first child -https://familysearch.org/ark:/61903/1:1:FQ7L-MY3The name Robert was previously used -https://familysearch.org/ark:/61903/1:1:FQP8-QW5JJThank you JJ!! And it helps her forename was simply Bell here too.