Wills was born on 19 August 1835 on the Molonglo Plain near modern-day Canberra, in the British penal colony (now the Australian state) of New South Wales, as the elder child of Horatio and Elizabeth (née McGuire) Wills.
Tom was a third-generation Australian of convict descent: his mother's parents were Irish convicts, and his paternal grandfather Edward was an English highwayman whose death sentence for armed robbery was commuted to transportation, arriving in Botany Bay aboard the "hell ship" Hillsborough in 1799.
Granted a conditional pardon in 1803, Edward became rich through mercantile activity in Sydney with his free wife Sarah (née Harding).
He died in 1811, five months before Horatio's birth, and Sarah remarried to convict George Howe, owner of Australia's first newspaper, The Sydney Gazette.
Mainly self-educated, Horatio worked in the Gazette office from a young age, rising to become editor in 1832, the same year he met Elizabeth, an orphan from Parramatta.
They married in December 1833.
Seventeen months after his birth, Tom was baptised Thomas Wentworth Wills in St Andrew's, Sydney, after statesman William Wentworth.
Drawing on Wentworth's pro-currency writings and the emancipist cause, Horatio, in his nationalist journal The Currency Lad (1832–33), made the first call for an Australian republic.

Horatio turned to pastoralism in the mid-1830s and moved with his family to the sheep run Burra Burra on the Molonglo River.
Tom was athletic early on but also prone to illness, his parents at one stage in 1839 "almost [despairing] of his recovery".
The following year, in light of Thomas Mitchell's discovery of "Australia Felix", the Willses, with shepherds and their families, overlanded south to the Grampians in the colony's Port Phillip District (now the state of Victoria).
After squatting on Mount William, they moved a few miles north through the foothills of Mount Ararat, named so by Horatio because "like the Ark, we rested there".
Horatio went through a period of intense religiosity while in the Grampians; at times his diary descends into incantation, "perhaps even madness" according to a number of scholarly assessments.
He implored himself and Tom to base their lives upon the New Testament.

Living in tents, the Wills family settled a large property named Lexington (near present-day Moyston) in an area used by Djab wurrung Aboriginal clans as a meeting place.
According to family members, Tom, as one of the few white children in the area, "was thrown much into the companionship of aborigines".
In an account of corroborees from childhood, his cousin H. C. A. Harrison remembered Tom's ability to learn Aboriginal songs, mimic their voice and gestures, and "speak their language as fluently as they did themselves, much to their delight."
He may have also played Aboriginal sports.
Horatio wrote fondly of his son's kinship with Aborigines, and allowed local clans to live and hunt on Lexington.
However, George Augustus Robinson, the district's Chief Protector of Aborigines, implicated Horatio and other local settlers in the murder of Aboriginals.
Horatio blamed "distant predatory tribes" for provoking hostilities in the area, and the closest he came to admitting that he had killed Aboriginals was in a letter to Governor Charles La Trobe: "... we shall be compelled in self defence to measures that may involve us in unpleasant consequences".

Tom's first sibling, Emily, was born on Christmas Day 1842.
In 1846 Wills began attendance at William Brickwood's School in Melbourne, where he lived with Horatio's brother Thomas (Tom's namesake), a Victorian separatist and son-in-law of the Wills family's partner in the shipping trade, convict Mary Reibey.
Tom played in his first cricket matches at school and came in contact with the Melbourne Cricket Club through Brickwood, the club's vice-president.
By 1849, the year Wills' schooling in Melbourne ended, his family had grown to include brothers Cedric, Horace and Egbert.
Horatio had ambitious plans for the education of his children, especially Tom:
I now deeply vainly deplore my want
Wills was born on 19 August 1835 on the Molonglo Plain near modern-day Canberra, in the British penal colony (now the Australian state) of New South Wales, as the elder child of Horatio and Elizabeth (née McGuire) Wills. Tom was a third-generation Australian of convict descent: his mother's parents were Irish convicts, and his paternal grandfather Edward was an English highwayman whose death sentence for armed robbery was commuted to transportation, arriving in Botany Bay aboard the "hell ship" Hillsborough in 1799. Granted a conditional pardon in 1803, Edward became rich through mercantile activity in Sydney with his free wife Sarah (née Harding). He died in 1811, five months before Horatio's birth, and Sarah remarried to convict George Howe, owner of Australia's first newspaper, The Sydney Gazette. Mainly self-educated, Horatio worked in the Gazette office from a young age, rising to become editor in 1832, the same year he met Elizabeth, an orphan from Parramatta. They married in December 1833. Seventeen months after his birth, Tom was baptised Thomas Wentworth Wills in St Andrew's, Sydney, after statesman William Wentworth. Drawing on Wentworth's pro-currency writings and the emancipist cause, Horatio, in his nationalist journal The Currency Lad (1832–33), made the first call for an Australian republic.
Horatio turned to pastoralism in the mid-1830s and moved with his family to the sheep run Burra Burra on the Molonglo River. Tom was athletic early on but also prone to illness, his parents at one stage in 1839 "almost [despairing] of his recovery". The following year, in light of Thomas Mitchell's discovery of "Australia Felix", the Willses, with shepherds and their families, overlanded south to the Grampians in the colony's Port Phillip District (now the state of Victoria). After squatting on Mount William, they moved a few miles north through the foothills of Mount Ararat, named so by Horatio because "like the Ark, we rested there". Horatio went through a period of intense religiosity while in the Grampians; at times his diary descends into incantation, "perhaps even madness" according to a number of scholarly assessments. He implored himself and Tom to base their lives upon the New Testament.
Living in tents, the Wills family settled a large property named Lexington (near present-day Moyston) in an area used by Djab wurrung Aboriginal clans as a meeting place. According to family members, Tom, as one of the few white children in the area, "was thrown much into the companionship of aborigines". In an account of corroborees from childhood, his cousin H. C. A. Harrison remembered Tom's ability to learn Aboriginal songs, mimic their voice and gestures, and "speak their language as fluently as they did themselves, much to their delight." He may have also played Aboriginal sports. Horatio wrote fondly of his son's kinship with Aborigines, and allowed local clans to live and hunt on Lexington. However, George Augustus Robinson, the district's Chief Protector of Aborigines, implicated Horatio and other local settlers in the murder of Aboriginals. Horatio blamed "distant predatory tribes" for provoking hostilities in the area, and the closest he came to admitting that he had killed Aboriginals was in a letter to Governor Charles La Trobe: "... we shall be compelled in self defence to measures that may involve us in unpleasant consequences".
Tom's first sibling, Emily, was born on Christmas Day 1842. In 1846 Wills began attendance at William Brickwood's School in Melbourne, where he lived with Horatio's brother Thomas (Tom's namesake), a Victorian separatist and son-in-law of the Wills family's partner in the shipping trade, convict Mary Reibey. Tom played in his first cricket matches at school and came in contact with the Melbourne Cricket Club through Brickwood, the club's vice-president. By 1849, the year Wills' schooling in Melbourne ended, his family had grown to include brothers Cedric, Horace and Egbert. Horatio had ambitious plans for the education of his children, especially Tom:
I now deeply vainly deplore my want 
Tom Wills