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.”

They would almost certainly have met in Paris, possibly in 1845, where Louise would have been living with her brother Emil, six years her junior, where she would have acted as mistress of his household. But by this time, he would probably have become betrothed to twenty-year old Amelie Cournol, whom he would wed in 1846. Two women in a household was bad luck. Louise was superfluous, and Emil would want her off his hands.

But what was Squire Holmes doing in Paris for the extended period necessary for courtship? Maybe it’s time to define “squire,” –a definition which by necessity is quite broad.

The large landowners—squires were all landowners—had hereditary estates, which varied in size which averaged about 10,000 acres, and drew enough income to build great parks and manors, keep servants and livery, and keep them in the style to which we’d all like to be accustomed. The estates in Sussex were mainly of this sort.

A rung below were the gentry, who typically owned less than 1,000 acres of land, who either leased plots to tenant farmers or managed farms themselves.

Slindon House

Let’s split the difference. We’ll imagine that Squire Holmes was the proprietor
of Slindon. Slindon Estate is 3,500 acres of woodland, downland, farmland, and parkland. With its unspoilt Sussex village, Slindon was originally the summer home of Stephen Langdon, Archbishop of Canterbury, whose election to the position helped precipitate the crisis which led to the signing of the Magna Carta. Slindon is seven miles from East Dean on the vast Gilbert Estate, where Holmes is supposed to have had his villa. The actual owner at the time in question was the Countess of Newburgh, but I’m sure she won’t mind lending it to us.

So why would Squire Holmes abandon this idyllic estate, with a house built during the reign of Elizabeth I? There are really only two possibilities which make sense. I’m afraid the most likely explanation is that he was in flight from creditors, and seeking a wealthy wife for an influx of new funds.

Alternatively he could have been fleeing from the legal consequences of a duel. Though dueling was outlawed in England in 1819, he last recorded duel in England took place in 1852—between two French expats. Dueling had become increasingly seen as a dishonorable means of setting disputes between gentlemen and more teeth had been put into the penalties for engaging in them. So I think we can eliminate this possibility.

How did the Squire’s ruin come to pass? In a word, no, two words, bad management. It would indirectly have been a result of the repeal of the Corn Laws in 1846, protectionist tariffs which had restricted the importation of grain.

Landowners were certain the repeal would make corn prices drop precipitously and reduce them all to penury. Coupled with the rise in wages for farm workers as more laborers moved to the cities, the squirearchy was forced to diversify, developing their land for housing, or mining. As a matter of fact, Thomas Read Kemp, an even larger Sussex landowner (and Member of Parliament), who was involved in some speculative land deals had to flee to Paris in 1837 and died there in 1844.

If Holmes had gambled on finding coal on his land and failed, he might have found new horizons in foreign countries extremely attractive. France was a favorite refuge for wealthier English debtors seeking to avoid prison.

La fidèle (1866)

Émile Vernet-Lecomte

And where to meet an artist but at the Paris Salon, the worls's grandest art exhibition, where in 1846 Emil won a bronze medal (his third), perhaps for one of his first portraits of an Oriental lady which he was to become famous for. The squire would have been in need of a moneyed wife, and LeComte at this point would have wanted to unburden himself of a sister (a sister who if she was anything like her son, would have been more intelligent and more domineering than his young wife could bear). It would not be long before the squire was introduced to Louise, and to her dowry, which would have been satisfactorily plump.

It would have been enough, anyway, for the squire to return safely to England with his new bride. And she would soon be pregnant and give birth to Mycroft.

The child is father to the man. What are we to make of indolent, overweight Mycroft, one of the founders that temple to silence, the Diogenes Club? This is what I would make of him: he probably had Einstein syndrome, named after the famous physicist, who did not speak in complete sentences till he was five years old. The syndrome is also accompanied by outstanding analytical skills. An indolent, silent child whose father probably thought him an idiot. Not a proper heir for the landed class. He looked forward to better.

What he got were miscarriages. And disappointment. And a fiery foreign wife who was no asset to him. Whether he sent her back to her people or whether she banged out the door of her own accord, whether Mycroft went with her (likely) or stayed with his father, she returned to Paris.

Sigerson's biography

Where, in 1854, she would have met eighteen-year-old George Sigerson. Now there’s a familiar name. George was an Irish lad, from county Tyrone. He was attending to St. Joseph’s College on the Rue de l’Enfer. George won 1st prize in drawing (perhaps tutored on the sly by Madame Holmes?), religious knowledge, and German, in 1854. He returned home after graduating in1855, winning first in Greek, Latin, and German (but not drawing). It would have been a May-September romance, understood as a brief fling by both of them. He likely never knew he had a child by Louise. As soon as she realized she was pregnant, she would have hied herself back to England and reconciliation with her husband, to make sure that her youngest son was legitimate.

George Sigerson went on to become a neurrologist, scientist, and one of the most prominent members of the Irish Literary Revival. He also became an important backer of Gaelic football. The Sigerson Cup is named for him. He married and had four (more) children. He probbably never suspected that the famous Sherlock Holmes was his son, although Sherlock must have discovered the truth and thought of himself in private as Sherlock Sigerson.

Exit George Sigerson.

So, why the distance between Sherlock and Mycroft? Besides their considerable age difference, they were only half-brothers. And I posited another reason in my first book, The Strange Case of Eliza Doolittle.

But why did neither inherit the estate? The squire must have had a child (or children) by his first wife, Hope (who died in childbirth), the elusive elder brother Sherrinford. Would he have got along with his younger siblings? Hard to say, but he certainly kept his distance. He would have inherited the bulk of the estate. The Squire would have used his influence to secure Mycroft a minor position with Her Majesty's government, from which he rose to great heights. Sherlock, whom the squire always suspected was no son of his, inherited only the clothes on his back. He was a natural mimic and seemed destined for a career in the theatre. There's a book somewhere in that.

The Strange Case of the Pharaoh's Heart cover

And that is truth about Sherlock's parentage--well, no it's not. Although the possibility is raised in my third book, The Strange Case of the Pharaoh's Heart, it's discredited, although the squire's paternity is also soundly rejected. Well, then, who was Sherlock's daddy, according to my lights? I'd rather not say, in case I get around to telling that tale. I have scattered a few clues in The Pharaoh's Heart, however, for the detectives among you.

*By the by, the name "Sigerson" means "son of victory." So put that in your pipe and smoke it.