Robert was born on 5 April 1800, the son of Kean Osborn, a white Jamaican planter of Scottish descent, and a woman of colour.
[3][4] In 1830, together with Jordon, he presented a petition to the Jamaican Assembly, which eventually agreed to grant free coloureds the rights to vote and to run for public office.
[6] In 1833, Osborn unsuccessfully ran in Saint Andrew Parish, Jamaica, losing by the margin of 74-22, but he reversed that result two years later.
[9][10] In 1861, Osborn disagreed with the governor, Charles Henry Darling, over some of policy decisions, and he made his opposition public through an editorial in The Morning Journal.
[11] In 1865, when governor Edward John Eyre abolished the Assembly following the Morant Bay Rebellion, Osborn strongly expressed his disapproval of the curtailment of Jamaica's democratic institutions.