I am also researching the Stuarts, for another project.
However, these Stuarts are very close cousins.
Henry Benson Stuart had a sister, Olivia. I don't have a birth date but on FindMyPast I found a marriage entry that is probably hers.
Calcutta, 1854. An Olivia Stuart married George Thomas Gowan.
The name is correct and so is the date - she would have been about 21 at this time.
I can find no entries for Gowan so would be delighted if someone else could.
My understanding is that Olivia, her husband and a child were killed in the Indian Mutiny in 1857.
It would be great to find out some more details... for a start I don't have any details about Olivia and Henry's mother, the wife of Col James Stuart.