Hello, Richard.
I believe I also am a direct decendant of Alexander Forbes and Cecilia Wilkie. My connection comes through my 4th-gr-grandfather, James Alexander Forbes, apparently one of their grandsons. He was the British vice-consul to Monterey, California, in the mid-nineteenth century. Based on information gleaned from a personal letter written by his son James Alonzo Forbes (my 3rd-gr-grandfather) to either a niece or his daughter, the Sir John Forbes (physician to the queen's household) was an uncle of his father's. Also, James Alexander Forbes (I refer to him as Grandpa James) had an uncle Alexander Forbes who was a merchant in Tepic, Mexico. When I was Googling to see if I could find information on this Sir John Forbes, I came across a website that was a bit of a biography on him, listed his parents as Alexander Forbes and Cecilia Wilkie, and mentioned that he had a brother Alexander who had made his fortune as a merchant in Mexico. Other sources of information about Alexander Forbes gave me his year of birth. Alexander Forbes (of Tepic, Mexico--I refer to him as Uncle Alexander) is credited with having written a book entitled "The History of Upper and Lower California", having sent it to be published by his brother John in London. This would have been in or around 1839. Anyway, based on these pieces of information, I believe I have the correct family for Grandpa James. The main branches of the Forbes family can be traced back to a Sir John de Forbes "of the Black Lip", and I am trying to pierce back as far as I can to find which branch our particular line goes through. Once the connection to Mr. "Black Lip" Forbes (what an identifier!) has been made, the Forbes family line can be traced quite a ways further back.
I live in Washington State in the US, and would be thrilled to swap information. It sounds like you may have more information than I have, but I would be happy to share what I have. Would you, by any chance, have any information on Alexander Forbes and Cecilia Wilkie at all? By Googling, I've been able to trace Cecilia Wilkie's family line back a bit but, except for what Millerina has kindly shared here at Rootschat, I've not been able to pierce back at all on Alexander Forbes.
Am eagerly waiting to hear back from you. Please take care and have a great day!
Blessings,
Linda Allen