Most people who search for “Guglielmo Ser Piero” are doing one thing — tracing a family tree. At some point, they landed on a name that connects, through genealogical records, to one of the most famous people who ever lived: Leonardo da Vinci.
So who exactly was Guglielmo di Ser Piero da Vinci? What do we actually know about him? And how does he fit into Leonardo’s family? This article walks through the confirmed facts, the limits of what history tells us, and why his name keeps appearing in genealogy databases today.
Who Guglielmo di Ser Piero da Vinci Was
According to genealogical records, Guglielmo di Ser Piero da Vinci was born around 1496 in Vinci, Firenze, Tuscany, Italy. His parents are listed as Piero Fruosino di Antonio da Vinci and Lucrezia Cortigiani.
That is, honestly, most of what we know about him directly. Outside of these basic vital records, there are no confirmed details about his occupation, his personal life, or any public role he may have played. No writings, no recorded achievements, no narrative account of his years.
It is important to be clear about that. The information we have on Guglielmo comes from genealogical compilations — sources like Ancestry.com — rather than detailed historical accounts or primary archival narratives. That does not mean the records are wrong, but it does mean they carry some uncertainty. Genealogy databases for Renaissance families can involve reconstructed trees, and individual entries should be treated as reasonable evidence, not absolute proof.
What those records do tell us, however, is meaningful — because his father’s identity connects him directly to Leonardo da Vinci.
His Father — Ser Piero da Vinci, Florentine Notary
To understand Guglielmo’s place in history, you need to understand his father first.
Ser Piero da Vinci’s full name was Ser Piero da Vinci d’Antonio di ser Piero di ser Guido. He was born on 19 April 1426 and died on 9 July 1504. His profession was that of a Florentine notary — a respected and well-paid role in Renaissance Italy, roughly equivalent to a combination of lawyer and official document keeper today.
The da Vinci family had a strong tradition in this profession. Genealogical and historical sources note that the family’s notarial history stretches back to a Ser Guido di Michele, with documented activity from as early as 1312. Multiple generations of da Vinci men worked as notaries, passing both the trade and the social standing down through the family line.
Ser Piero himself married at least four times over the course of his life. He had numerous legitimate children across those marriages, in addition to Leonardo, who was born outside of marriage. This pattern of multiple unions across several decades is what makes the da Vinci family tree large, and at times confusing, for modern researchers trying to follow it.
Guglielmo’s Place in Leonardo da Vinci’s Family
Now for the question most readers are really asking: was Guglielmo related to Leonardo, and how?
Yes — based on available genealogical records, Guglielmo was Leonardo da Vinci’s half-brother. Here is how that works.
Leonardo was born on 15 April 1452. He was the illegitimate son of Ser Piero and a woman from Vinci commonly identified as Caterina. Guglielmo, born around 1496, was a later legitimate son of the same Ser Piero — but from a different mother, Lucrezia Cortigiani. They shared a father. That makes them half-brothers.
The age gap between them is striking. Leonardo was around 44 years older than Guglielmo. By the time Guglielmo was born, Leonardo was already a well-established artist and thinker, known across Italy. The two half-brothers belonged to entirely different chapters of Ser Piero’s life.
Think of it like a modern blended family. A father marries more than once, has children with different partners, and ends up with a wide spread of offspring who may barely know one another. Some are decades apart in age. Some grew up in different households. Ser Piero’s family was not so different — except the time period was 15th-century Tuscany, and the documentation we have today is thin.
Guglielmo Was Not the Only Late Child
Guglielmo was not an isolated entry in the records. Genealogical sources also list a child named Benedetto di Ser Piero da Vinci, born around 1492 in Vinci, to the same parents — Piero Fruosino di Antonio da Vinci and Lucrezia Cortigiani. That puts Benedetto about four years older than Guglielmo.
This tells us that Guglielmo was part of a small group of children born late in Ser Piero’s life, all through his union with Lucrezia Cortigiani. They were among the youngest half-siblings in an already large family.
A Note on Another Child Named Guglielmo
There is one complication worth flagging — especially if you are doing your own genealogical research on this family.
A scholarly article on death and burial in Leonardo’s family records that on 5 December 1486, Ser Piero buried a baby boy named Guglielmo Francesco in the family tomb. The child died less than six weeks after birth.
That means there were, at minimum, two children in Ser Piero’s household who bore a version of the name Guglielmo — one who died as an infant in 1486, and one born around 1496 who appears in later genealogical records. This kind of naming repetition was not unusual in Renaissance families, where the same name might be given again after a child died young.
If you are building or checking a family tree, it is worth being careful here. Guglielmo Francesco, who died in 1486, is a different person from the Guglielmo born in 1496. The dates and the middle name are what help tell them apart.
Why Guglielmo Appears in Genealogy Databases Today
Most people encounter Guglielmo di Ser Piero da Vinci because they are browsing platforms like Ancestry, MyHeritage, or Geni while researching their family history. They come across a name, see it linked to “Piero Fruosino di Antonio da Vinci,” and wonder whether they have found a branch of Leonardo da Vinci’s family.
The short answer is: yes, if Guglielmo’s entry is correctly linked to Ser Piero, then he does sit on the same family tree as Leonardo. They shared the same father. But it is worth double-checking any genealogy platform’s data against multiple sources, because user-submitted trees can sometimes include errors or gaps — especially for records going back five centuries.
For most casual researchers, the connection is real enough: Guglielmo was one of Ser Piero’s later children, born during the final decade of the notary’s life, and is legitimately identified as a half-brother of Leonardo da Vinci through genealogical records.
What Life Might Have Looked Like for Guglielmo
We do not know what Guglielmo did with his life. No confirmed records describe his adult years, his profession, or his descendants. It is entirely possible — even likely — that he lived and died in relative obscurity, as most people do.
What we can say is that children of Florentine notary families in the late 15th century typically grew up in a world shaped by law, commerce, and civic life. Sons of notaries often followed the same path, entering the legal and administrative trades that formed the backbone of Florentine professional society. Whether Guglielmo did the same, we simply do not know.
If you are interested in exploring how Renaissance families like the da Vincis are being researched and documented today, resources like Bubiz Business cover a wide range of historical and cultural topics worth exploring.
Final Thoughts
Guglielmo di Ser Piero da Vinci is not a famous figure. He left no art, no writings, and no public legacy that history has preserved. What he left is a name in a genealogical record, tied to one of the most documented Renaissance families in Italian history.
His significance, such as it is, comes from his father — Ser Piero da Vinci, the Florentine notary who fathered Leonardo da Vinci decades earlier. Through that shared father, Guglielmo sits on the same family tree as one of history’s most extraordinary minds, even if he himself remains largely unknown.
For genealogy researchers, that connection is worth understanding clearly. For everyone else, Guglielmo’s story is a quiet reminder that even the most famous family trees are full of ordinary people — living ordinary lives, mostly undocumented, just a few branches away from greatness.
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