Just one James Latta baptised 1743-1761 in Dumbarton and this was in 1743 to a John Latta & Jean Davie : I feel this is unlikely our James, as quite old for a 1781 marriage and our James does not use the name John for a son- just Robert & William
James Latta married Katharine Lang in 1781 Dumbarton -FS
They had Robert 1781, William 1783 & Robert 1785 all baptised Dumbarton.