These people would not be in my direct line, I don't think, but I've got a William R.J. Niven, druggist apprentice, boarding with a family of Meins in Glasgow in 1861. He was born in Jamaica. He may have been apprenticed to Dr Alexander Meldrum Forman, druggist and surgeon, on High Street in Glasgow.
In 1871 William's sister Jane was living with him. A year older than he, she was born around 1843 in Jamaica. As of 1881 she was still unmarried and living next door to William and his wife, Elizabeth, in Edinburgh.
The last trace I find of them is living on Marmion Terrace in Newington, Edinburgh, in 1881. William Niven is now married to Elizabeth, surname unknown, who'd been born around 1859 in Old Calabar, Jamaica. They married sometime between 1871 and 1881.
Perhaps they returned to Jamaica? Did they have any family connections to the Formans or the Meins (or the Bells) in Scotland?