The Hamersleys were a well connected family, and he was related by blood or marriage to a number of prominent Western Australian farmers and politicians.

His father, Edward, was one of the leading Western Australian landholders of his day; his brother Edward also became a Member of the Legislative Council; William Locke Brockman was his uncle; his sister Margaret married Sir John Forrest; and his wife Matilda was sister to Maitland Brown.

From about 1865 until 1868, he managed the family's Richmond property at Williams; he then spend some time at Wungong in the Canning district, before returning to Guildford in 1870.

In 1873, he was running a butchering business, and in 1875 he inherited his father's Haseley property in Toodyay.

The following May, he won the seat of Swan in a by-election, but was only required to hold it for five months before the Legislative Council was reformed with the advent of responsible government.