Firstly I suppose I should say that the following is mere conjecture, though pretty thoroughly researched as far as it goes. But I don't actually believe a large part of it myself, having even more outlandish theories up my sleeve. I just can't resist starting a few hares.
I suppose the first question we should ask is this: why does Sherlock Holmes never mentions his parents, not even if they are alive or dead? It seems strange, doesn’t it? Here are a few more questions which follow:
- Why is Sherlock so distant from his brother Mycroft?
- Why are the brothers separated in age by seven years?
- Why did neither of the brothers inherit their father's estate?
- Why did he choose the name Sigerson as his alias?
Well, then, what do we know about Holmes’s parents? Very little. We know from The Adventure of the Greek Interpreter that: “My ancestors were country squires, who appear to have led much the same life as is natural to their class."
Let’s assume for the moment that his father was one such squire (although it’s interesting the way he phrases it, skirting actual mention of his father). Let’s call him Squire Holmes. Perhaps he is a Sussex landowner, since Holmes elects to retire in Sussex. We’ll come back to him.
We know a little more of Sherlock’s mother, however, since he goes on to mention “my grandmother, who was the sister of Vernet, the French artist.” Vernet, the French artist was a very real person, or rather very real people, a family of artists who mainly married into other artistic families, all quite successful. Let’s take a look at the generations:
- Jean Vernet, d. 1753
- Claude Vernet, d. 1789
- Carle Vernet, d. 1836
- Horace Vernet, d. 1863
While two of his forebears had sisters (Jean had five, but they lived early enough that Holmes would have referred to them as great or even great-great grandmothers. Carle's sister Emilie, was guillotined during the Terror. Her daughter Louise-Josephe, was married twice, but neither of her husbands were named Holmes, according to the genealogies. Claude had only brothers.
So it’s almost certainly Horace Vernet that Holmes was referring to. And while the fame of Vernet has been swept away by Manet, Monet, and the rest of the Impressionists, it’s worth noting that he was in his time the most famous of French painters, fabulously successful.
Only Horace’s sister, Camille (b. 1788 d. 1858) therefore, could be his grandmother. Camille wed Hippolyte LeComte, another successful painter, and had three children: Emil (another painter), Fanny (another painter), and Louise. Genealogical records are silent on whether Louise was also a painter (and silent on everything about her other than her name and birthdate), but there can be little doubt she knew her way around an easel.
Fanny was born in 1809, Louise in 1815. Since Sherlock was born (according to most chronologists) in 1854, that would mean Louise would have had him at the age of 39—a dangerous age to give birth, especially in the Victorian era. Indeed, her first child, Mycroft, would have been born when she was 32. We can eliminate Fanny from our calculations. At 45, she almost certainly would have been too old for childbirth. Even at Louse’s age, childbirth would have been a dangerous proposition.
Perhaps the reason no other siblings are mentioned is that Mrs. Holmes had a number of miscarriages? This would certainly explain the age gap between the two brothers.
But how would this tame English squire and the bohemian French lady ever have met? And why marry? I’m afraid it was not for love, although Louise Vernet-LeComte was probably a fascinating woman, even though, in the parlance, an “old maid.”