Hamish was born into the wizarding Buchanan family sometime during the mid-19th century and grew up in a village in the Scottish Borders. He was his parents' first- or second-born son, and had a total of ten siblings, including his sister Flora and his younger brother Angus. All of the Buchanan children had a reputation for being of above-average size and behaving wildly.
When Hamish turned eleven, he received a Hogwarts acceptance letter, and began attending Hogwarts School of Witchcraft and Wizardry. The local Muggle villagers, not knowing that the Buchanan family were magical, assumed that he had been sent to a corrective facility or mental institution.
Hamish and his other siblings were especially fond of their brother Angus. Since their father was highly prejudiced against Squibs, Hamish and his siblings covered for Angus when, unlike them, he displayed no signs of magical ability. On 1 September, 1858, the day that eleven-year-old Angus was due to begin his first year at Hogwarts, Hamish flew him to Hogwarts Castle on the back of his broomstick, desperately hoping that the faculty would allow him to stay once he arrived, or that the school might be able to coax some magic out of him.
- Pottermore (Mentioned only)